# Gauge Charts — full content > A free reference for shop and trade measurements: sheet metal gauge to thickness for steel, stainless, galvanised and aluminium, American Wire Gauge with NEC ampacity, every fractional, number, letter and metric drill size, tap drill sizes with the thread engagement each one actually gives, and a NEC Chapter 9 conduit fill calculator. This document aggregates the reference content of https://gaugecharts.com/ for AI ingestion. Canonical URLs are listed per section — cite the URL, not this file. --- ## Sheet Metal Gauge Chart: Steel, Alu, SS Canonical: https://gaugecharts.com/ Sheet metal gauge to thickness for steel, stainless, galvanised and aluminium, in inches and millimetres, with a live lookup and sheet weight. Each material uses a different standard, which is why one gauge number has four answers. --- ## 1/4-20 Tap Drill Size Canonical: https://gaugecharts.com/tap-drill-size/1-4-20 The tap drill for a 1/4-20 thread is #7, which is 0.2010 inches or 5.11 mm. That leaves approximately 75% thread engagement. The close-fit clearance drill for a 1/4-20 fastener is 17/64 (0.2656 inches). The default general-purpose coarse thread in the inch system. Machine screws, jigs and fixtures, T-slot tables, camera and tripod hardware in the 1/4-20 form, and most shop-built weldments. --- ## 10-32 Tap Drill Size Canonical: https://gaugecharts.com/tap-drill-size/10-32 The tap drill for a 10-32 thread is #21, which is 0.1590 inches or 4.04 mm. That leaves approximately 76% thread engagement. The close-fit clearance drill for a 10-32 fastener is #11 (0.1910 inches). The fine-thread partner to 10-24, and the standard rack-mount thread in EIA-310 equipment racks. Also common in avionics, electronics chassis and anywhere vibration resistance matters. --- ## 10-24 Tap Drill Size Canonical: https://gaugecharts.com/tap-drill-size/10-24 The tap drill for a 10-24 thread is #25, which is 0.1495 inches or 3.80 mm. That leaves approximately 75% thread engagement. The close-fit clearance drill for a 10-24 fastener is #11 (0.1910 inches). The coarse-thread number 10, common in sheet metal assemblies, electrical panels and general fabrication where the mating material is softer. --- ## M6 x 1.0 Tap Drill Size Canonical: https://gaugecharts.com/tap-drill-size/m6 The tap drill for a M6 x 1.0 thread is 5.0 mm, which is 0.1969 inches or 5.00 mm. That leaves approximately 92% thread engagement. The close-fit clearance drill for a M6 x 1.0 fastener is 6.4 mm (0.2520 inches). The most common metric fastener in machinery, bicycles, automotive brackets and flat-pack furniture inserts. The metric equivalent in size to 1/4-20, though not interchangeable with it. --- ## M8 x 1.25 Tap Drill Size Canonical: https://gaugecharts.com/tap-drill-size/m8 The tap drill for a M8 x 1.25 thread is 6.8 mm, which is 0.2677 inches or 6.80 mm. That leaves approximately 89% thread engagement. The close-fit clearance drill for a M8 x 1.25 fastener is 8.4 mm (0.3307 inches). The general-purpose metric thread one size up from M6. Engine ancillaries, machine frames, motor mounts and structural brackets. --- ## 1/2-13 Tap Drill Size Canonical: https://gaugecharts.com/tap-drill-size/1-2-13 The tap drill for a 1/2-13 thread is 27/64, which is 0.4219 inches or 10.72 mm. That leaves approximately 78% thread engagement. The close-fit clearance drill for a 1/2-13 fastener is 33/64 (0.5156 inches). The workhorse coarse thread for structural bolting, machine feet, threaded rod and anchor hardware in the inch system. --- ## M10 x 1.5 Tap Drill Size Canonical: https://gaugecharts.com/tap-drill-size/m10 The tap drill for a M10 x 1.5 thread is 8.5 mm, which is 0.3346 inches or 8.50 mm. That leaves approximately 92% thread engagement. The close-fit clearance drill for a M10 x 1.5 fastener is 10.5 mm (0.4134 inches). Structural metric bolting, suspension components, engine mounts and heavy machine assembly. --- ## 5/16-18 Tap Drill Size Canonical: https://gaugecharts.com/tap-drill-size/5-16-18 The tap drill for a 5/16-18 thread is F, which is 0.2570 inches or 6.53 mm. That leaves approximately 77% thread engagement. The close-fit clearance drill for a 5/16-18 fastener is 21/64 (0.3281 inches). The coarse thread one size up from 1/4-20, and the usual choice for brackets, machine guards, trailer hardware and light structural work where 1/4 inch is not quite enough. --- ## 3/8-16 Tap Drill Size Canonical: https://gaugecharts.com/tap-drill-size/3-8-16 The tap drill for a 3/8-16 thread is 5/16, which is 0.3125 inches or 7.94 mm. That leaves approximately 77% thread engagement. The close-fit clearance drill for a 3/8-16 fastener is 25/64 (0.3906 inches). Structural inch bolting: machine bases, motor mounts, heavy brackets, trailer and towing hardware. The point where a tap handle stops being enough and a tapping head starts to help. --- ## 7/16-14 Tap Drill Size Canonical: https://gaugecharts.com/tap-drill-size/7-16-14 The tap drill for a 7/16-14 thread is U, which is 0.3680 inches or 9.35 mm. That leaves approximately 75% thread engagement. The close-fit clearance drill for a 7/16-14 fastener is 29/64 (0.4531 inches). An intermediate structural size, common in older American machinery, agricultural equipment and automotive chassis work. --- ## M3 x 0.5 Tap Drill Size Canonical: https://gaugecharts.com/tap-drill-size/m3 The tap drill for a M3 x 0.5 thread is 2.5 mm, which is 0.0984 inches or 2.50 mm. That leaves approximately 92% thread engagement. The close-fit clearance drill for a M3 x 0.5 fastener is 3.2 mm (0.1260 inches). The standard small metric fastener in electronics, 3D printer frames, camera hardware, PCB standoffs and consumer product assembly. --- ## M4 x 0.7 Tap Drill Size Canonical: https://gaugecharts.com/tap-drill-size/m4 The tap drill for a M4 x 0.7 thread is 3.3 mm, which is 0.1299 inches or 3.30 mm. That leaves approximately 93% thread engagement. The close-fit clearance drill for a M4 x 0.7 fastener is 4.3 mm (0.1693 inches). Small metric machine screws in electronics enclosures, appliance assembly, bicycle accessories and light brackets. --- ## M5 x 0.8 Tap Drill Size Canonical: https://gaugecharts.com/tap-drill-size/m5 The tap drill for a M5 x 0.8 thread is 4.2 mm, which is 0.1654 inches or 4.20 mm. That leaves approximately 92% thread engagement. The close-fit clearance drill for a M5 x 0.8 fastener is 5.3 mm (0.2087 inches). Bicycle bottle cages and accessory mounts, furniture fittings, appliance panels and general light metric assembly. --- ## M12 x 1.75 Tap Drill Size Canonical: https://gaugecharts.com/tap-drill-size/m12 The tap drill for a M12 x 1.75 thread is 10.2 mm, which is 0.4016 inches or 10.20 mm. That leaves approximately 95% thread engagement. The close-fit clearance drill for a M12 x 1.75 fastener is 13.0 mm (0.5118 inches). Heavy structural metric fastening: machine bases, towing components, lifting eyes and chassis work. --- ## 14 Gauge Steel Thickness Canonical: https://gaugecharts.com/steel-gauge-thickness/14 14 gauge steel is 0.0747 inches thick, which is 1.90 mm. One square foot weighs 3.05 lb, so a 4x8 sheet is about 98 lb. Structural brackets, weldments, trailer decking, tool boxes, smoker and firebox bodies, and machine guarding that has to take a knock. --- ## 11 Gauge Steel Thickness Canonical: https://gaugecharts.com/steel-gauge-thickness/11 11 gauge steel is 0.1196 inches thick, which is 3.04 mm. One square foot weighs 4.88 lb, so a 4x8 sheet is about 156 lb. Heavy fabrication: gussets, base plates, hitch reinforcement, bumper brackets and anything that will be welded and loaded. --- ## 16 Gauge Steel Thickness Canonical: https://gaugecharts.com/steel-gauge-thickness/16 16 gauge steel is 0.0598 inches thick, which is 1.52 mm. One square foot weighs 2.44 lb, so a 4x8 sheet is about 78 lb. The general-purpose sheet gauge. Ductwork, enclosures, panels, automotive patch panels, brackets and most shop projects. --- ## 10 Gauge Steel Thickness Canonical: https://gaugecharts.com/steel-gauge-thickness/10 10 gauge steel is 0.1345 inches thick, which is 3.42 mm. One square foot weighs 5.49 lb, so a 4x8 sheet is about 176 lb. Heavy plate work below quarter inch: skid plates, trailer tongues, machine frames and wear surfaces. --- ## 12 Gauge Steel Thickness Canonical: https://gaugecharts.com/steel-gauge-thickness/12 12 gauge steel is 0.1046 inches thick, which is 2.66 mm. One square foot weighs 4.27 lb, so a 4x8 sheet is about 137 lb. Structural sheet: shelving, racking, machine frames, security panels and heavy enclosures. --- ## 18 Gauge Steel Thickness Canonical: https://gaugecharts.com/steel-gauge-thickness/18 18 gauge steel is 0.0478 inches thick, which is 1.21 mm. One square foot weighs 1.95 lb, so a 4x8 sheet is about 62 lb. Light enclosures, ductwork, automotive body panels, kick plates and appliance skins. --- ## 7 Gauge Steel Thickness Canonical: https://gaugecharts.com/steel-gauge-thickness/7 7 gauge steel is 0.1793 inches thick, which is 4.55 mm. One square foot weighs 7.32 lb, so a 4x8 sheet is about 234 lb. Near-plate work: heavy machine bases, press frames, ballistic and wear plate, and structural gussets. --- ## 20 Gauge Steel Thickness Canonical: https://gaugecharts.com/steel-gauge-thickness/20 20 gauge steel is 0.0359 inches thick, which is 0.91 mm. One square foot weighs 1.47 lb, so a 4x8 sheet is about 47 lb. Light ductwork, flashing, drip edge, decorative panels and general sheet metal work. --- ## 22 Gauge Steel Thickness Canonical: https://gaugecharts.com/steel-gauge-thickness/22 22 gauge steel is 0.0299 inches thick, which is 0.76 mm. One square foot weighs 1.22 lb, so a 4x8 sheet is about 39 lb. Flashing, roofing accessories, light duct and craft or hobby metalwork. --- ## 24 Gauge Steel Thickness Canonical: https://gaugecharts.com/steel-gauge-thickness/24 24 gauge steel is 0.0239 inches thick, which is 0.61 mm. One square foot weighs 0.98 lb, so a 4x8 sheet is about 31 lb. Roof flashing, HVAC duct, sign blanks and light enclosures. --- ## 13 Gauge Steel Thickness Canonical: https://gaugecharts.com/steel-gauge-thickness/13 13 gauge steel is 0.0897 inches thick, which is 2.28 mm. One square foot weighs 3.66 lb, so a 4x8 sheet is about 117 lb. Between 12 and 14 gauge work: brackets, frames and heavier enclosures where 14 flexes. --- ## Wire Size for 50 Amps Canonical: https://gaugecharts.com/wire-size/50-amps A 50 amp circuit requires 8 AWG copper at the 75 degree C column of NEC Table 310.16, or 6 AWG aluminium. At 60 degree C terminations it is 6 AWG copper. Electric ranges and cooktops, RV shore power, welders, hot tubs and Level 2 EV chargers rated at 40 A continuous. A 50 A circuit feeding a continuous load, which includes an EV charger, must be sized at 125 percent of that load under NEC 210.19(A)(1), so a 40 A continuous charger is exactly what a 50 A circuit is for. --- ## Wire Size for 100 Amps Canonical: https://gaugecharts.com/wire-size/100-amps A 100 amp circuit requires 3 AWG copper at the 75 degree C column of NEC Table 310.16, or 1 AWG aluminium. At 60 degree C terminations it is 1 AWG copper. Subpanels, detached garages and workshops, small dwelling services and larger HVAC equipment. Most 100 A panels and breakers carry 75 degree C terminations, but check: a 60 degree C rating forces the 60 degree column and pushes you from 3 AWG copper to 1 AWG. --- ## Wire Size for 60 Amps Canonical: https://gaugecharts.com/wire-size/60-amps A 60 amp circuit requires 6 AWG copper at the 75 degree C column of NEC Table 310.16, or 4 AWG aluminium. At 60 degree C terminations it is 4 AWG copper. Small subpanels, electric furnaces, large air conditioners and workshop feeders. Sixty amps is the point where aluminium starts to make economic sense on longer runs, at 4 AWG against 6 AWG copper. --- ## Wire Size for 30 Amps Canonical: https://gaugecharts.com/wire-size/30-amps A 30 amp circuit requires 10 AWG copper at the 75 degree C column of NEC Table 310.16, or 10 AWG aluminium. At 60 degree C terminations it is 10 AWG copper. Electric dryers, water heaters, small welders, RV 30 A service and window air conditioners. NEC 240.4(D) caps 10 AWG copper at 30 A regardless of insulation rating, so 10 AWG is both the minimum and the practical maximum use for this circuit. --- ## Wire Size for 40 Amps Canonical: https://gaugecharts.com/wire-size/40-amps A 40 amp circuit requires 8 AWG copper at the 75 degree C column of NEC Table 310.16, or 8 AWG aluminium. At 60 degree C terminations it is 8 AWG copper. Electric ranges in smaller kitchens, large water heaters, and Level 2 EV chargers rated 32 A continuous. Eight AWG copper is 40 A only in the 60 degree column and 50 A at 75 degrees, so the termination rating decides whether 8 AWG is comfortable or marginal here. --- ## Wire Size for 200 Amps Canonical: https://gaugecharts.com/wire-size/200-amps A 200 amp circuit requires 3/0 AWG copper at the 75 degree C column of NEC Table 310.16, or larger AWG aluminium. At 60 degree C terminations it is larger AWG copper. Standard modern dwelling service, large subpanels and shop services. Two hundred amp services are commonly run in 2/0 copper or 4/0 aluminium. Service entrance conductors may use NEC 310.12 dwelling ratios, which permit smaller conductors than Table 310.16 alone. --- ## Wire Size for 20 Amps Canonical: https://gaugecharts.com/wire-size/20-amps A 20 amp circuit requires 12 AWG copper at the 75 degree C column of NEC Table 310.16, or 12 AWG aluminium. At 60 degree C terminations it is 12 AWG copper. Kitchen and bathroom small-appliance circuits, garage and workshop receptacles, and most general-purpose 120 V branch circuits. NEC 240.4(D) caps 12 AWG copper at 20 A. Do not use 14 AWG on a 20 A breaker under any circumstances; it is the single most common residential wiring violation. --- ## Wire Size for 125 Amps Canonical: https://gaugecharts.com/wire-size/125-amps A 125 amp circuit requires 1 AWG copper at the 75 degree C column of NEC Table 310.16, or 2/0 AWG aluminium. At 60 degree C terminations it is 1/0 AWG copper. Large subpanels, small commercial services and heavy shop feeders. At 125 A the jump is to 1/0 copper or 2/0 aluminium at 75 degrees C. Voltage drop starts to dominate on feeder runs beyond about 100 feet. --- ## Wire Size for 80 Amps Canonical: https://gaugecharts.com/wire-size/80-amps A 80 amp circuit requires 4 AWG copper at the 75 degree C column of NEC Table 310.16, or 2 AWG aluminium. At 60 degree C terminations it is 3 AWG copper. Large subpanels, commercial HVAC and heavy workshop equipment. Eighty amps is not a standard breaker size in NEC 240.6(A) below 100 A in every product line, so confirm the breaker exists before designing around it. --- ## Wire Size for 150 Amps Canonical: https://gaugecharts.com/wire-size/150-amps A 150 amp circuit requires 1/0 AWG copper at the 75 degree C column of NEC Table 310.16, or 3/0 AWG aluminium. At 60 degree C terminations it is 3/0 AWG copper. Dwelling services on smaller homes, large subpanels and commercial feeders. One hundred and fifty amp services commonly use 1/0 copper or 2/0 aluminium, with NEC 310.12 dwelling ratios often permitting one size smaller for service conductors. --- ## Wire Size for 70 Amps Canonical: https://gaugecharts.com/wire-size/70-amps A 70 amp circuit requires 4 AWG copper at the 75 degree C column of NEC Table 310.16, or 3 AWG aluminium. At 60 degree C terminations it is 4 AWG copper. Subpanels, electric furnaces and larger workshop feeders. Four AWG copper covers 70 A at 75 degrees C with margin, which is why 70 A circuits are often run in the same conductor as 85 A ones. --- ## Wire Size for 15 Amps Canonical: https://gaugecharts.com/wire-size/15-amps A 15 amp circuit requires 14 AWG copper at the 75 degree C column of NEC Table 310.16, or 12 AWG aluminium. At 60 degree C terminations it is 14 AWG copper. Lighting circuits, general receptacles in bedrooms and living areas, and most residential branch circuits in older homes. NEC 240.4(D) caps 14 AWG copper at 15 A. Fourteen AWG is the smallest conductor permitted for a general branch circuit in a dwelling. --- ## Wire Gauge Chart: AWG Sizes Canonical: https://gaugecharts.com/wire-gauge-chart American Wire Gauge runs backwards: the smaller the number, the thicker the wire. 4/0 is the largest size in common building work at 0.4600 inches, and each step up in gauge number is about 89 percent of the previous diameter, so six gauge numbers roughly halves the diameter and cuts the cross-sectional area by four. ### AWG size chart Diameters and areas are fixed by the AWG definition, a geometric series between 4/0 at 0.4600 inches and 36 AWG at 0.0050 inches. Resistance is NEC Chapter 9, Table 8 for uncoated copper at 75 degrees C. | AWG | Diameter (in) | Diameter (mm) | Area (cmil) | Area (mm2) | Ohms/1000 ft | | --- | --- | --- | --- | --- | --- | | 24 | 0.0201 | 0.51 | 404 | 0.20 | 25.67 | | 22 | 0.0253 | 0.64 | 640 | 0.32 | 16.14 | | 20 | 0.0320 | 0.81 | 1,020 | 0.52 | 10.15 | | 18 | 0.0403 | 1.02 | 1,620 | 0.82 | 7.95 | | 16 | 0.0508 | 1.29 | 2,580 | 1.31 | 4.99 | | 14 | 0.0641 | 1.63 | 4,110 | 2.08 | 3.14 | | 12 | 0.0808 | 2.05 | 6,530 | 3.31 | 1.98 | | 10 | 0.1019 | 2.59 | 10,380 | 5.26 | 1.24 | | 8 | 0.1285 | 3.26 | 16,510 | 8.37 | 0.778 | | 6 | 0.1620 | 4.11 | 26,240 | 13.30 | 0.491 | | 4 | 0.2043 | 5.19 | 41,740 | 21.15 | 0.308 | | 3 | 0.2294 | 5.83 | 52,620 | 26.70 | 0.245 | | 2 | 0.2576 | 6.54 | 66,360 | 33.60 | 0.194 | | 1 | 0.2893 | 7.35 | 83,690 | 42.40 | 0.154 | | 1/0 | 0.3249 | 8.25 | 105,600 | 53.50 | 0.122 | | 2/0 | 0.3648 | 9.27 | 133,100 | 67.40 | 0.0967 | | 3/0 | 0.4096 | 10.40 | 167,800 | 85.00 | 0.0766 | | 4/0 | 0.4600 | 11.68 | 211,600 | 107.20 | 0.0608 | ### How the AWG numbers work - The scale is geometric, not linear. Every gauge step multiplies the diameter by about 0.8905. - Three gauge steps roughly halves the cross-sectional area. Six steps halves the diameter. - Sizes above 1 AWG are written 1/0, 2/0, 3/0 and 4/0, spoken as "one aught" through "four aught". They keep getting thicker in that order. - Past 4/0 the scale stops and conductors are specified in thousands of circular mils (kcmil) instead. - Stranded and solid wire of the same AWG have the same cross-sectional area of copper, but stranded has a slightly larger overall diameter. ### Wire terms, defined **Ampacity**: The maximum current a conductor can carry continuously without exceeding its temperature rating. It is a property of the conductor, its insulation and its surroundings, not of the circuit. **Circular mil**: The area of a circle one thousandth of an inch in diameter. Conductor area in circular mils is simply the diameter in mils squared, which is why the unit exists. **Aught**: The spoken form of the zero in sizes above 1 AWG. 1/0 is "one aught", 4/0 is "four aught", and each one is thicker than the last. **kcmil**: Thousands of circular mils. Conductors larger than 4/0 leave the AWG scale and are specified this way instead, starting at 250 kcmil. **Derating**: Reducing a conductor's table ampacity to account for high ambient temperature or for more than three current-carrying conductors sharing a raceway. ### Common questions **Is a higher gauge number thicker or thinner wire?** Thinner. The AWG scale runs backwards, so 20 AWG is thinner than 10 AWG. The numbering comes from the drawing process: a wire pulled through more successive dies gets a higher number and a smaller diameter. **How many amps can 12 gauge wire carry?** NEC Table 310.16 lists 12 AWG copper at 20 A in the 60 degree C column, 25 A at 75 degrees C and 30 A at 90 degrees C. In practice NEC 240.4(D) caps the overcurrent protection for 12 AWG copper at 20 A regardless of insulation, so a 20 A breaker is the normal answer. **What is the difference between AWG and mm2?** AWG is a gauge number on a fixed geometric scale; mm2 is the actual cross-sectional area. They are not interchangeable, and no AWG size lands exactly on a standard metric size. 12 AWG is 3.31 mm2, which sits between the 2.5 mm2 and 4 mm2 metric conductors. --- ## Ampacity Chart: NEC Table 310.16 Canonical: https://gaugecharts.com/ampacity-chart Ampacity is the current a conductor can carry continuously without exceeding its temperature rating. NEC Table 310.16 is the starting point for conductors in a raceway or cable, and it assumes not more than three current-carrying conductors and an ambient temperature of 30 degrees C. Every real installation then needs three further checks before the table value can be used. ### NEC Table 310.16 ampacity Values are for insulated conductors rated 0 to 2000 V, not more than three current-carrying conductors in a raceway, cable or earth, at an ambient of 30 degrees C. | AWG | Cu 60 °C | Cu 75 °C | Cu 90 °C | Al 60 °C | Al 75 °C | Al 90 °C | | --- | --- | --- | --- | --- | --- | --- | | 18 | – | – | 14 | – | – | – | | 16 | – | – | 18 | – | – | – | | 14 | 15 | 20 | 25 | – | – | – | | 12 | 20 | 25 | 30 | 15 | 20 | 25 | | 10 | 30 | 35 | 40 | 25 | 30 | 35 | | 8 | 40 | 50 | 55 | 35 | 40 | 45 | | 6 | 55 | 65 | 75 | 40 | 50 | 55 | | 4 | 70 | 85 | 95 | 55 | 65 | 75 | | 3 | 85 | 100 | 115 | 65 | 75 | 85 | | 2 | 95 | 115 | 130 | 75 | 90 | 100 | | 1 | 110 | 130 | 145 | 85 | 100 | 115 | | 1/0 | 125 | 150 | 170 | 100 | 120 | 135 | | 2/0 | 145 | 175 | 195 | 115 | 135 | 150 | | 3/0 | 165 | 200 | 225 | 130 | 155 | 175 | | 4/0 | 195 | 230 | 260 | 150 | 180 | 205 | ### The three corrections the table does not include A number read straight off Table 310.16 is almost never the installed ampacity. These are the adjustments the code requires, and skipping them is the most common way a correct-looking chart lookup produces a non-compliant circuit. 1. Correct for ambient temperature: NEC 310.15(B)(1). Above 30 degrees C the conductor carries less. An attic at 50 degrees C derates a 90 degree C conductor to 82 percent of the table value. 2. Adjust for conductor count: NEC 310.15(C)(1). Four to six current-carrying conductors in one raceway derate to 80 percent, seven to nine to 70 percent, ten to twenty to 50 percent. Neutrals that carry only unbalanced current do not count; neutrals on a three-phase four-wire circuit supplying non-linear loads do. 3. Limit to the lowest-rated termination: NEC 110.14(C). Equipment rated for 60 degrees C forces you to use the 60 degree C column even if the wire itself is 90 degree C THHN. Most breakers and devices at 100 A or less are 60 or 75 degrees C rated. This single rule catches more mistakes than the other two combined. NEC 240.4(D) adds a fourth constraint that is not a derating at all but a hard cap: overcurrent protection for 14 AWG copper may not exceed 15 A, for 12 AWG 20 A, and for 10 AWG 30 A, whatever the ampacity table says. This is why a 12 AWG conductor listed at 25 A in the 75 degree column is still protected by a 20 A breaker on an ordinary branch circuit. ### Common questions **What size wire do I need for 50 amps?** For a 50 A circuit, 8 AWG copper at the 75 degree C column carries 50 A and is the usual answer, or 6 AWG aluminium. If the terminations are only rated 60 degrees C, 8 AWG copper is listed at 40 A and you need 6 AWG copper instead. Long runs may need a size up for voltage drop. **Why does the same wire have three different ampacities?** Because the limit is temperature, not current. A conductor with 90 degree C insulation can run hotter before the insulation degrades, so it carries more current. You can only use the higher column if every termination in the circuit is also rated for that temperature, which NEC 110.14(C) usually prevents. **Does Table 310.16 apply to wire in free air?** No. Table 310.16 is for conductors in a raceway, cable or directly buried. Single conductors in free air use Table 310.17, which gives substantially higher values because heat escapes more easily. --- ## Wire Size Calculator: Amps to AWG Canonical: https://gaugecharts.com/wire-size-calculator The minimum conductor for a load is the smallest size whose NEC Table 310.16 ampacity meets the load at the insulation rating you are actually allowed to use. Long runs are then often limited by voltage drop rather than by heat, which is why a 100 foot circuit sometimes needs a larger conductor than the ampacity table alone would suggest. ### Wire size by circuit amps The minimum conductor for each common breaker size, with the NEC 240.4(D) small-conductor cap applied. Use the 60 degree C column unless every termination in the circuit is listed for 75 degrees, which NEC 110.14(C) requires you to confirm. | Circuit | Copper 60 °C | Copper 75 °C | Aluminium 75 °C | | --- | --- | --- | --- | | 15 A | 14 | 14 | 12 | | 20 A | 12 | 12 | 12 | | 30 A | 10 | 10 | 10 | | 40 A | 8 | 8 | 8 | | 50 A | 6 | 8 | 6 | | 60 A | 4 | 6 | 4 | | 70 A | 4 | 4 | 3 | | 80 A | 3 | 4 | 2 | | 100 A | 1 | 3 | 1 | | 125 A | 1/0 | 1 | 2/0 | | 150 A | 3/0 | 1/0 | 3/0 | | 200 A | – | 3/0 | – | ### How voltage drop is calculated Voltage drop over a single-phase run is Vd = 2 × K × I × L / cmil, where K is 12.9 for copper and 21.2 for aluminium, I is the current in amps, L is the one-way run in feet, and cmil is the conductor area in circular mils. The 2 accounts for current travelling out and back. For three-phase, replace the 2 with 1.732. The NEC does not require a voltage drop limit on ordinary branch circuits. It recommends 3 percent for a branch circuit and 5 percent total including the feeder, in the informational notes to 210.19(A) and 215.2(A). Those notes are advice, not rules, but equipment behaves badly at the end of a long undersized run, and motors in particular draw more current at reduced voltage, which heats the conductor further. ### Common questions **What size wire do I need for a 100 amp subpanel?** For 100 A at the 75 degree C column, 3 AWG copper is listed at 100 A and 1 AWG aluminium at 100 A. Many installers use 2 AWG copper or 1/0 aluminium for margin and for voltage drop on longer feeder runs. Check that the panel and breaker terminations are rated 75 degrees C before using that column. **Does wire size depend on the length of the run?** Ampacity does not, but the usable size often does. Ampacity is set by heat and is independent of length. Voltage drop rises directly with length, so beyond roughly 100 feet it frequently becomes the deciding factor and pushes you one or two sizes up. --- ## Conduit Fill Calculator: NEC Chapter 9 Tables Canonical: https://gaugecharts.com/conduit-fill-calculator The National Electrical Code limits how much of a conduit cross-section conductors may occupy: 53 percent for a single conductor, 31 percent for exactly two, and 40 percent for three or more. The limits exist so conductors can be pulled without damaging insulation and so heat can escape, which is why the two-conductor case is stricter than the three-conductor case rather than looser. ### Allowable fill area at 40 percent Total internal areas are NEC Chapter 9, Table 4. The figures below are those areas at the 40 percent limit that applies to three or more conductors, which covers almost all real installations. | Trade size | EMT | IMC | RMC (rigid) | PVC Sch 40 | PVC Sch 80 | | --- | --- | --- | --- | --- | --- | | 1/2" | 0.122 | 0.137 | 0.126 | 0.114 | 0.087 | | 3/4" | 0.213 | 0.234 | 0.220 | 0.203 | 0.164 | | 1" | 0.346 | 0.384 | 0.355 | 0.333 | 0.275 | | 1-1/4" | 0.598 | 0.659 | 0.610 | 0.581 | 0.495 | | 1-1/2" | 0.814 | 0.890 | 0.828 | 0.794 | 0.684 | | 2" | 1.342 | 1.452 | 1.363 | 1.316 | 1.150 | | 2-1/2" | 2.343 | 2.054 | 1.946 | 1.878 | 1.648 | | 3" | 3.538 | 3.169 | 3.000 | 2.907 | 2.577 | | 3-1/2" | 4.618 | 4.234 | 4.004 | 3.895 | 3.475 | | 4" | 5.901 | 5.452 | 5.153 | 5.022 | 4.503 | ### Conductor areas Add up the area of every conductor going into the raceway, including the equipment grounding conductor, and compare the total with the allowable area above. | AWG | THHN / THWN-2 | XHHW / XHHW-2 | | --- | --- | --- | | 1 | 0.1562 | 0.1534 | | 2 | 0.1158 | 0.1146 | | 3 | 0.0973 | 0.0962 | | 4 | 0.0824 | 0.0814 | | 6 | 0.0507 | 0.0590 | | 8 | 0.0366 | 0.0437 | | 10 | 0.0211 | 0.0243 | | 12 | 0.0133 | 0.0181 | | 14 | 0.0097 | 0.0139 | | 1/0 | 0.1855 | 0.1825 | | 2/0 | 0.2223 | 0.2190 | | 3/0 | 0.2679 | 0.2642 | | 4/0 | 0.3237 | 0.3197 | ### Common questions **How many 12 AWG THHN wires fit in 1/2 inch EMT?** Nine. Half-inch EMT has 0.304 square inches of internal area, so the 40 percent limit is 0.1216 square inches. A 12 AWG THHN conductor is 0.0133 square inches, and nine of them come to 0.1197 square inches, which fits. A tenth would take it to 0.1330 and exceed the limit. **Does the ground wire count toward conduit fill?** Yes. Every conductor in the raceway counts toward fill, including equipment grounding conductors and neutrals. A bare ground counts too, using its bare cross-sectional area rather than an insulated area. **Why is the limit for two conductors lower than for three?** Because of the jamming risk when pulling. Two round conductors in a round conduit can wedge against each other and the conduit wall in a way that three or more cannot, so the code sets 31 percent for exactly two and 40 percent once there are three or more. --- ## Drill Bit Size Chart & Decimals Canonical: https://gaugecharts.com/drill-bit-size-chart Twist drills come in four overlapping series, and a full index contains all of them because the gaps in any one series are too coarse for close work. Fractional sizes step by 1/64 inch, number sizes fill the range from 0.0135 up to 0.228 inches, letter sizes carry on from 0.234 to 0.413 inches, and metric drills interleave with all three. ### All drill sizes by diameter Sorted by actual diameter so the next size up or down is always the next row, whichever series it belongs to. Fractional sizes are exact by definition; number and letter decimals are the ANSI standard values. | Size | Series | Inches | mm | | --- | --- | --- | --- | | #80 | Number | 0.0135 | 0.34 | | #79 | Number | 0.0145 | 0.37 | | 1/64 | Fractional | 0.0156 | 0.40 | | #78 | Number | 0.0160 | 0.41 | | #77 | Number | 0.0180 | 0.46 | | #76 | Number | 0.0200 | 0.51 | | #75 | Number | 0.0210 | 0.53 | | #74 | Number | 0.0225 | 0.57 | | #73 | Number | 0.0240 | 0.61 | | #72 | Number | 0.0250 | 0.64 | | #71 | Number | 0.0260 | 0.66 | | #70 | Number | 0.0280 | 0.71 | | #69 | Number | 0.0292 | 0.74 | | #68 | Number | 0.0310 | 0.79 | | 1/32 | Fractional | 0.0313 | 0.79 | | #67 | Number | 0.0320 | 0.81 | | #66 | Number | 0.0330 | 0.84 | | #65 | Number | 0.0350 | 0.89 | | #64 | Number | 0.0360 | 0.91 | | #63 | Number | 0.0370 | 0.94 | | #62 | Number | 0.0380 | 0.97 | | #61 | Number | 0.0390 | 0.99 | | 1 mm | Metric | 0.0394 | 1.00 | | #60 | Number | 0.0400 | 1.02 | | #59 | Number | 0.0410 | 1.04 | | #58 | Number | 0.0420 | 1.07 | | #57 | Number | 0.0430 | 1.09 | | #56 | Number | 0.0465 | 1.18 | | 3/64 | Fractional | 0.0469 | 1.19 | | #55 | Number | 0.0520 | 1.32 | | #54 | Number | 0.0550 | 1.40 | | 1.5 mm | Metric | 0.0591 | 1.50 | | #53 | Number | 0.0595 | 1.51 | | 1/16 | Fractional | 0.0625 | 1.59 | | #52 | Number | 0.0635 | 1.61 | | #51 | Number | 0.0670 | 1.70 | | #50 | Number | 0.0700 | 1.78 | | #49 | Number | 0.0730 | 1.85 | | #48 | Number | 0.0760 | 1.93 | | 5/64 | Fractional | 0.0781 | 1.98 | | #47 | Number | 0.0785 | 1.99 | | 2 mm | Metric | 0.0787 | 2.00 | | #46 | Number | 0.0810 | 2.06 | | #45 | Number | 0.0820 | 2.08 | | #44 | Number | 0.0860 | 2.18 | | 2.2 mm | Metric | 0.0866 | 2.20 | | #43 | Number | 0.0890 | 2.26 | | #42 | Number | 0.0935 | 2.37 | | 3/32 | Fractional | 0.0938 | 2.38 | | 2.4 mm | Metric | 0.0945 | 2.40 | | #41 | Number | 0.0960 | 2.44 | | #40 | Number | 0.0980 | 2.49 | | 2.5 mm | Metric | 0.0984 | 2.50 | | #39 | Number | 0.0995 | 2.53 | | #38 | Number | 0.1015 | 2.58 | | #37 | Number | 0.1040 | 2.64 | | #36 | Number | 0.1065 | 2.71 | | 7/64 | Fractional | 0.1094 | 2.78 | | #35 | Number | 0.1100 | 2.79 | | #34 | Number | 0.1110 | 2.82 | | #33 | Number | 0.1130 | 2.87 | | #32 | Number | 0.1160 | 2.95 | | 3 mm | Metric | 0.1181 | 3.00 | | #31 | Number | 0.1200 | 3.05 | | 1/8 | Fractional | 0.1250 | 3.17 | | 3.2 mm | Metric | 0.1260 | 3.20 | | #30 | Number | 0.1285 | 3.26 | | 3.3 mm | Metric | 0.1299 | 3.30 | | 3.4 mm | Metric | 0.1339 | 3.40 | | #29 | Number | 0.1360 | 3.45 | | 3.5 mm | Metric | 0.1378 | 3.50 | | #28 | Number | 0.1405 | 3.57 | | 9/64 | Fractional | 0.1406 | 3.57 | | #27 | Number | 0.1440 | 3.66 | | #26 | Number | 0.1470 | 3.73 | | #25 | Number | 0.1495 | 3.80 | | #24 | Number | 0.1520 | 3.86 | | #23 | Number | 0.1540 | 3.91 | | 5/32 | Fractional | 0.1563 | 3.97 | | #22 | Number | 0.1570 | 3.99 | | 4 mm | Metric | 0.1575 | 4.00 | | #21 | Number | 0.1590 | 4.04 | | #20 | Number | 0.1610 | 4.09 | | 4.2 mm | Metric | 0.1654 | 4.20 | | #19 | Number | 0.1660 | 4.22 | | 4.3 mm | Metric | 0.1693 | 4.30 | | #18 | Number | 0.1695 | 4.31 | | 11/64 | Fractional | 0.1719 | 4.37 | | #17 | Number | 0.1730 | 4.39 | | #16 | Number | 0.1770 | 4.50 | | 4.5 mm | Metric | 0.1772 | 4.50 | | #15 | Number | 0.1800 | 4.57 | | #14 | Number | 0.1820 | 4.62 | | #13 | Number | 0.1850 | 4.70 | | 3/16 | Fractional | 0.1875 | 4.76 | | 4.8 mm | Metric | 0.1890 | 4.80 | | #12 | Number | 0.1890 | 4.80 | | #11 | Number | 0.1910 | 4.85 | | #10 | Number | 0.1935 | 4.91 | | #9 | Number | 0.1960 | 4.98 | | 5 mm | Metric | 0.1969 | 5.00 | | #8 | Number | 0.1990 | 5.05 | | #7 | Number | 0.2010 | 5.11 | | 13/64 | Fractional | 0.2031 | 5.16 | | #6 | Number | 0.2040 | 5.18 | | #5 | Number | 0.2055 | 5.22 | | 5.3 mm | Metric | 0.2087 | 5.30 | | #4 | Number | 0.2090 | 5.31 | | #3 | Number | 0.2130 | 5.41 | | 5.5 mm | Metric | 0.2165 | 5.50 | | 7/32 | Fractional | 0.2188 | 5.56 | | #2 | Number | 0.2210 | 5.61 | | #1 | Number | 0.2280 | 5.79 | | 5.8 mm | Metric | 0.2283 | 5.80 | | A | Letter | 0.2340 | 5.94 | | 15/64 | Fractional | 0.2344 | 5.95 | | 6 mm | Metric | 0.2362 | 6.00 | | B | Letter | 0.2380 | 6.05 | | C | Letter | 0.2420 | 6.15 | | D | Letter | 0.2460 | 6.25 | | 1/4 | Fractional | 0.2500 | 6.35 | | E | Letter | 0.2500 | 6.35 | | 6.4 mm | Metric | 0.2520 | 6.40 | | 6.5 mm | Metric | 0.2559 | 6.50 | | F | Letter | 0.2570 | 6.53 | | 6.6 mm | Metric | 0.2598 | 6.60 | | G | Letter | 0.2610 | 6.63 | | 17/64 | Fractional | 0.2656 | 6.75 | | H | Letter | 0.2660 | 6.76 | | 6.8 mm | Metric | 0.2677 | 6.80 | | I | Letter | 0.2720 | 6.91 | | 7 mm | Metric | 0.2756 | 7.00 | | J | Letter | 0.2770 | 7.04 | | K | Letter | 0.2810 | 7.14 | | 9/32 | Fractional | 0.2813 | 7.14 | | L | Letter | 0.2900 | 7.37 | | M | Letter | 0.2950 | 7.49 | | 7.5 mm | Metric | 0.2953 | 7.50 | | 19/64 | Fractional | 0.2969 | 7.54 | | N | Letter | 0.3020 | 7.67 | | 5/16 | Fractional | 0.3125 | 7.94 | | 8 mm | Metric | 0.3150 | 8.00 | | O | Letter | 0.3160 | 8.03 | | P | Letter | 0.3230 | 8.20 | | 21/64 | Fractional | 0.3281 | 8.33 | | 8.4 mm | Metric | 0.3307 | 8.40 | | Q | Letter | 0.3320 | 8.43 | | 8.5 mm | Metric | 0.3346 | 8.50 | | R | Letter | 0.3390 | 8.61 | | 11/32 | Fractional | 0.3438 | 8.73 | | S | Letter | 0.3480 | 8.84 | | 9 mm | Metric | 0.3543 | 9.00 | | T | Letter | 0.3580 | 9.09 | | 23/64 | Fractional | 0.3594 | 9.13 | | U | Letter | 0.3680 | 9.35 | | 9.5 mm | Metric | 0.3740 | 9.50 | | 3/8 | Fractional | 0.3750 | 9.52 | | V | Letter | 0.3770 | 9.58 | | W | Letter | 0.3860 | 9.80 | | 25/64 | Fractional | 0.3906 | 9.92 | | 10 mm | Metric | 0.3937 | 10.00 | | X | Letter | 0.3970 | 10.08 | | 10.2 mm | Metric | 0.4016 | 10.20 | | Y | Letter | 0.4040 | 10.26 | | 13/32 | Fractional | 0.4063 | 10.32 | | Z | Letter | 0.4130 | 10.49 | | 10.5 mm | Metric | 0.4134 | 10.50 | | 27/64 | Fractional | 0.4219 | 10.72 | | 11 mm | Metric | 0.4331 | 11.00 | | 7/16 | Fractional | 0.4375 | 11.11 | | 11.5 mm | Metric | 0.4528 | 11.50 | | 29/64 | Fractional | 0.4531 | 11.51 | | 15/32 | Fractional | 0.4688 | 11.91 | | 12 mm | Metric | 0.4724 | 12.00 | | 31/64 | Fractional | 0.4844 | 12.30 | | 12.5 mm | Metric | 0.4921 | 12.50 | | 1/2 | Fractional | 0.5000 | 12.70 | | 13 mm | Metric | 0.5118 | 13.00 | | 33/64 | Fractional | 0.5156 | 13.10 | | 17/32 | Fractional | 0.5313 | 13.49 | | 13.5 mm | Metric | 0.5315 | 13.50 | | 35/64 | Fractional | 0.5469 | 13.89 | | 14 mm | Metric | 0.5512 | 14.00 | | 9/16 | Fractional | 0.5625 | 14.29 | | 14.5 mm | Metric | 0.5709 | 14.50 | | 37/64 | Fractional | 0.5781 | 14.68 | | 15 mm | Metric | 0.5906 | 15.00 | | 19/32 | Fractional | 0.5938 | 15.08 | | 39/64 | Fractional | 0.6094 | 15.48 | | 15.5 mm | Metric | 0.6102 | 15.50 | | 5/8 | Fractional | 0.6250 | 15.88 | | 16 mm | Metric | 0.6299 | 16.00 | | 41/64 | Fractional | 0.6406 | 16.27 | | 16.5 mm | Metric | 0.6496 | 16.50 | | 21/32 | Fractional | 0.6563 | 16.67 | | 17 mm | Metric | 0.6693 | 17.00 | | 43/64 | Fractional | 0.6719 | 17.07 | | 11/16 | Fractional | 0.6875 | 17.46 | | 17.5 mm | Metric | 0.6890 | 17.50 | | 45/64 | Fractional | 0.7031 | 17.86 | | 18 mm | Metric | 0.7087 | 18.00 | | 23/32 | Fractional | 0.7188 | 18.26 | | 47/64 | Fractional | 0.7344 | 18.65 | | 3/4 | Fractional | 0.7500 | 19.05 | | 49/64 | Fractional | 0.7656 | 19.45 | | 25/32 | Fractional | 0.7813 | 19.84 | | 51/64 | Fractional | 0.7969 | 20.24 | | 13/16 | Fractional | 0.8125 | 20.64 | | 53/64 | Fractional | 0.8281 | 21.03 | | 27/32 | Fractional | 0.8438 | 21.43 | | 55/64 | Fractional | 0.8594 | 21.83 | | 7/8 | Fractional | 0.8750 | 22.22 | | 57/64 | Fractional | 0.8906 | 22.62 | | 29/32 | Fractional | 0.9063 | 23.02 | | 59/64 | Fractional | 0.9219 | 23.42 | | 15/16 | Fractional | 0.9375 | 23.81 | | 61/64 | Fractional | 0.9531 | 24.21 | | 31/32 | Fractional | 0.9688 | 24.61 | | 63/64 | Fractional | 0.9844 | 25.00 | | 1 | Fractional | 1.0000 | 25.40 | | 1-1/64 | Fractional | 1.0156 | 25.80 | | 1-1/32 | Fractional | 1.0313 | 26.19 | | 1-3/64 | Fractional | 1.0469 | 26.59 | | 1-1/16 | Fractional | 1.0625 | 26.99 | | 1-5/64 | Fractional | 1.0781 | 27.38 | | 1-3/32 | Fractional | 1.0938 | 27.78 | | 1-7/64 | Fractional | 1.1094 | 28.18 | | 1-1/8 | Fractional | 1.1250 | 28.57 | | 1-9/64 | Fractional | 1.1406 | 28.97 | | 1-5/32 | Fractional | 1.1563 | 29.37 | | 1-11/64 | Fractional | 1.1719 | 29.77 | | 1-3/16 | Fractional | 1.1875 | 30.16 | | 1-13/64 | Fractional | 1.2031 | 30.56 | | 1-7/32 | Fractional | 1.2188 | 30.96 | | 1-15/64 | Fractional | 1.2344 | 31.35 | | 1-1/4 | Fractional | 1.2500 | 31.75 | | 1-17/64 | Fractional | 1.2656 | 32.15 | | 1-9/32 | Fractional | 1.2813 | 32.54 | | 1-19/64 | Fractional | 1.2969 | 32.94 | | 1-5/16 | Fractional | 1.3125 | 33.34 | | 1-21/64 | Fractional | 1.3281 | 33.73 | | 1-11/32 | Fractional | 1.3438 | 34.13 | | 1-23/64 | Fractional | 1.3594 | 34.53 | | 1-3/8 | Fractional | 1.3750 | 34.92 | | 1-25/64 | Fractional | 1.3906 | 35.32 | | 1-13/32 | Fractional | 1.4063 | 35.72 | | 1-27/64 | Fractional | 1.4219 | 36.12 | | 1-7/16 | Fractional | 1.4375 | 36.51 | | 1-29/64 | Fractional | 1.4531 | 36.91 | | 1-15/32 | Fractional | 1.4688 | 37.31 | | 1-31/64 | Fractional | 1.4844 | 37.70 | | 1-1/2 | Fractional | 1.5000 | 38.10 | ### Common questions **What order do number drill sizes go in?** Backwards, like wire gauge. Number 1 is the largest at 0.228 inches and number 80 is the smallest at 0.0135 inches. Letter sizes run the other way: A is the smallest at 0.234 inches and Z the largest at 0.413 inches. **What is the metric equivalent of a 1/4 inch drill?** A quarter inch is 6.35 mm exactly. The nearest common metric drills are 6.5 mm, which is 0.2559 inches and slightly oversize, and 6.0 mm, which is 0.2362 inches and undersize. There is no exact metric equivalent. --- ## Tap Drill Chart: UNC, UNF, Metric Canonical: https://gaugecharts.com/tap-drill-chart Inch and metric tap drills follow two different conventions, and most charts publish them under one heading as though they did not. Inch tap drills target about 75 percent thread engagement. The metric rule is to subtract the pitch from the diameter, so M6 by 1.0 takes a 5.0 mm drill, and that lands at about 92 percent. Both are the stocked standard, and the table below shows what each listed drill actually gives. ### Tap drill and clearance sizes | Thread | Series | Tap drill | Inches | % thread | Clearance (close) | | --- | --- | --- | --- | --- | --- | | #0-80 | UNF (fine) | 3/64 | 0.0469 | 81% | #51 | | #2-56 | UNC (coarse) | #50 | 0.0700 | 69% | #43 | | #4-40 | UNC (coarse) | #43 | 0.0890 | 71% | #33 | | #6-32 | UNC (coarse) | #36 | 0.1065 | 78% | #28 | | #8-32 | UNC (coarse) | #29 | 0.1360 | 69% | #19 | | #10-24 | UNC (coarse) | #25 | 0.1495 | 75% | #11 | | #10-32 | UNF (fine) | #21 | 0.1590 | 76% | #11 | | #12-24 | UNC (coarse) | #16 | 0.1770 | 72% | #2 | | 1/4-20 | UNC (coarse) | #7 | 0.2010 | 75% | 17/64 | | 1/4-28 | UNF (fine) | #3 | 0.2130 | 80% | 17/64 | | 5/16-18 | UNC (coarse) | F | 0.2570 | 77% | 21/64 | | 5/16-24 | UNF (fine) | I | 0.2720 | 75% | 21/64 | | 3/8-16 | UNC (coarse) | 5/16 | 0.3125 | 77% | 25/64 | | 3/8-24 | UNF (fine) | Q | 0.3320 | 79% | 25/64 | | 7/16-14 | UNC (coarse) | U | 0.3680 | 75% | 29/64 | | 7/16-20 | UNF (fine) | 25/64 | 0.3906 | 72% | 29/64 | | 1/2-13 | UNC (coarse) | 27/64 | 0.4219 | 78% | 33/64 | | 1/2-20 | UNF (fine) | 29/64 | 0.4531 | 72% | 33/64 | | 9/16-12 | UNC (coarse) | 31/64 | 0.4844 | 72% | 37/64 | | 5/8-11 | UNC (coarse) | 17/32 | 0.5312 | 79% | 41/64 | | 5/8-18 | UNF (fine) | 37/64 | 0.5781 | 65% | 41/64 | | 3/4-10 | UNC (coarse) | 21/32 | 0.6562 | 72% | 49/64 | | 3/4-16 | UNF (fine) | 11/16 | 0.6875 | 77% | 49/64 | | 7/8-9 | UNC (coarse) | 49/64 | 0.7656 | 76% | 57/64 | | 1-8 | UNC (coarse) | 7/8 | 0.8750 | 77% | 1-1/32 | | M2 × 0.4 | Metric coarse | 1.6 mm | 0.0630 | 92% | 2.2 mm | | M3 × 0.5 | Metric coarse | 2.5 mm | 0.0984 | 92% | 3.2 mm | | M4 × 0.7 | Metric coarse | 3.3 mm | 0.1299 | 93% | 4.3 mm | | M5 × 0.8 | Metric coarse | 4.2 mm | 0.1654 | 92% | 5.3 mm | | M6 × 1.0 | Metric coarse | 5.0 mm | 0.1969 | 92% | 6.4 mm | | M8 × 1.25 | Metric coarse | 6.8 mm | 0.2677 | 89% | 8.4 mm | | M10 × 1.5 | Metric coarse | 8.5 mm | 0.3346 | 92% | 10.5 mm | | M12 × 1.75 | Metric coarse | 10.2 mm | 0.4016 | 95% | 13.0 mm | | M14 × 2.0 | Metric coarse | 12.0 mm | 0.4724 | 92% | 15.0 mm | | M16 × 2.0 | Metric coarse | 14.0 mm | 0.5512 | 92% | 17.0 mm | ### Working out a tap drill for any engagement For unified threads the drill diameter is the major diameter minus the engagement fraction times 1.299 divided by threads per inch. For metric it is the major diameter minus the engagement fraction times the pitch times 1.0825. A 1/4-20 thread has a major diameter of 0.250 inches and 20 threads per inch. At 75 percent engagement the theoretical drill is 0.250 minus 0.75 times 1.299 divided by 20, which is 0.2013 inches. The nearest standard drill is a number 7 at 0.201 inches, which is what every chart lists. Softer materials such as aluminium and brass tolerate higher engagement because the tap cuts more easily. Harder materials and deep blind holes are usually tapped at 60 to 65 percent to keep torque down, which is exactly the case where a broken tap costs the most to remove. ### Common questions **What size drill for a 1/4-20 tap?** A number 7 drill, which is 0.201 inches. That gives about 75 percent thread engagement. If you do not have a number set, 13/64 at 0.2031 inches is slightly larger and gives about 72 percent, which is acceptable for most work. **What is the tap drill for M8 x 1.25?** A 6.8 mm drill. The rule for ISO metric coarse threads is to subtract the pitch from the major diameter, so 8 minus 1.25 gives 6.75 mm and 6.8 mm is the nearest standard drill. Note that this lands at about 89 percent thread engagement rather than the 75 percent an inch tap drill targets, because metric and inch follow different conventions. **Why do metric tap drills give more thread engagement than inch ones?** Because they follow different conventions. Inch tap drill charts are built around roughly 75 percent engagement. The metric convention is simply to subtract the pitch from the major diameter, which works out at about 92 percent. Neither is wrong, but a metric tap cuts noticeably harder than an inch tap of similar size, and in tough material many shops go up a tenth or two of a millimetre to bring it closer to 75 percent. **Why not tap to 100 percent thread?** Because it adds almost nothing and costs a great deal. Going from 75 to 100 percent engagement increases thread strength by roughly 5 percent while more than doubling the tapping torque. In practice the fastener fails before a 75 percent thread strips. --- ## Fraction to Decimal Chart: Inches in 64ths Canonical: https://gaugecharts.com/fraction-to-decimal-chart Inch fractions on a tape measure divide down in halves: 1/2, 1/4, 1/8, 1/16, 1/32 and 1/64. The table below lists all 64 positions with the decimal and millimetre equivalent, which is what you need when a drawing is dimensioned in decimals and your tape is not. ### Inch fractions, decimals and millimetres | Fraction | Decimal (in) | mm | | --- | --- | --- | | 1/64 | 0.0156 | 0.397 | | 1/32 | 0.0313 | 0.794 | | 3/64 | 0.0469 | 1.191 | | 1/16 | 0.0625 | 1.587 | | 5/64 | 0.0781 | 1.984 | | 3/32 | 0.0938 | 2.381 | | 7/64 | 0.1094 | 2.778 | | 1/8 | 0.1250 | 3.175 | | 9/64 | 0.1406 | 3.572 | | 5/32 | 0.1563 | 3.969 | | 11/64 | 0.1719 | 4.366 | | 3/16 | 0.1875 | 4.762 | | 13/64 | 0.2031 | 5.159 | | 7/32 | 0.2188 | 5.556 | | 15/64 | 0.2344 | 5.953 | | 1/4 | 0.2500 | 6.350 | | 17/64 | 0.2656 | 6.747 | | 9/32 | 0.2813 | 7.144 | | 19/64 | 0.2969 | 7.541 | | 5/16 | 0.3125 | 7.938 | | 21/64 | 0.3281 | 8.334 | | 11/32 | 0.3438 | 8.731 | | 23/64 | 0.3594 | 9.128 | | 3/8 | 0.3750 | 9.525 | | 25/64 | 0.3906 | 9.922 | | 13/32 | 0.4063 | 10.319 | | 27/64 | 0.4219 | 10.716 | | 7/16 | 0.4375 | 11.112 | | 29/64 | 0.4531 | 11.509 | | 15/32 | 0.4688 | 11.906 | | 31/64 | 0.4844 | 12.303 | | 1/2 | 0.5000 | 12.700 | | 33/64 | 0.5156 | 13.097 | | 17/32 | 0.5313 | 13.494 | | 35/64 | 0.5469 | 13.891 | | 9/16 | 0.5625 | 14.287 | | 37/64 | 0.5781 | 14.684 | | 19/32 | 0.5938 | 15.081 | | 39/64 | 0.6094 | 15.478 | | 5/8 | 0.6250 | 15.875 | | 41/64 | 0.6406 | 16.272 | | 21/32 | 0.6563 | 16.669 | | 43/64 | 0.6719 | 17.066 | | 11/16 | 0.6875 | 17.462 | | 45/64 | 0.7031 | 17.859 | | 23/32 | 0.7188 | 18.256 | | 47/64 | 0.7344 | 18.653 | | 3/4 | 0.7500 | 19.050 | | 49/64 | 0.7656 | 19.447 | | 25/32 | 0.7813 | 19.844 | | 51/64 | 0.7969 | 20.241 | | 13/16 | 0.8125 | 20.637 | | 53/64 | 0.8281 | 21.034 | | 27/32 | 0.8438 | 21.431 | | 55/64 | 0.8594 | 21.828 | | 7/8 | 0.8750 | 22.225 | | 57/64 | 0.8906 | 22.622 | | 29/32 | 0.9063 | 23.019 | | 59/64 | 0.9219 | 23.416 | | 15/16 | 0.9375 | 23.813 | | 61/64 | 0.9531 | 24.209 | | 31/32 | 0.9688 | 24.606 | | 63/64 | 0.9844 | 25.003 | | 1/1 | 1.0000 | 25.400 | ### Common questions **How do I convert a fraction to a decimal?** Divide the top number by the bottom number. Three-eighths is 3 divided by 8, which is 0.375 inches. To go to millimetres, multiply the decimal by 25.4, so 0.375 inches is 9.525 mm. **What is 0.0625 as a fraction?** One sixteenth. Multiply by 64 to get the number of 64ths, so 0.0625 times 64 is 4, giving 4/64, which reduces to 1/16. --- ## Steel Sheet Weight by Gauge Canonical: https://gaugecharts.com/steel-weight-calculator The Manufacturers Standard Gauge for sheet steel is defined by weight rather than by thickness. Each gauge number is a nominal weight per square foot, converted to a thickness using 41.82 pounds per square foot per inch. That constant comes from wrought iron, not modern steel, so the thicknesses it defines are exact but the weights below are calculated from the real density of steel, 0.2836 pounds per cubic inch, which gives 40.84 rather than 41.82. ### Steel sheet weight by gauge | Gauge | Inches | mm | lb/ft2 | | --- | --- | --- | --- | | 3 | 0.2391 | 6.07 | 9.76 | | 4 | 0.2242 | 5.69 | 9.16 | | 5 | 0.2092 | 5.31 | 8.54 | | 6 | 0.1943 | 4.94 | 7.93 | | 7 | 0.1793 | 4.55 | 7.32 | | 8 | 0.1644 | 4.18 | 6.71 | | 9 | 0.1495 | 3.80 | 6.11 | | 10 | 0.1345 | 3.42 | 5.49 | | 11 | 0.1196 | 3.04 | 4.88 | | 12 | 0.1046 | 2.66 | 4.27 | | 13 | 0.0897 | 2.28 | 3.66 | | 14 | 0.0747 | 1.90 | 3.05 | | 15 | 0.0673 | 1.71 | 2.75 | | 16 | 0.0598 | 1.52 | 2.44 | | 17 | 0.0538 | 1.37 | 2.20 | | 18 | 0.0478 | 1.21 | 1.95 | | 19 | 0.0418 | 1.06 | 1.71 | | 20 | 0.0359 | 0.91 | 1.47 | | 21 | 0.0329 | 0.84 | 1.34 | | 22 | 0.0299 | 0.76 | 1.22 | | 23 | 0.0269 | 0.68 | 1.10 | | 24 | 0.0239 | 0.61 | 0.98 | | 25 | 0.0209 | 0.53 | 0.85 | | 26 | 0.0179 | 0.45 | 0.73 | | 27 | 0.0164 | 0.42 | 0.67 | | 28 | 0.0149 | 0.38 | 0.61 | | 29 | 0.0135 | 0.34 | 0.55 | | 30 | 0.0120 | 0.30 | 0.49 | ### Common questions **How much does a 4x8 sheet of 16 gauge steel weigh?** About 78 pounds. Sixteen gauge steel is 0.0598 inches thick and weighs 2.44 pounds per square foot at the real density of steel, and a 4 foot by 8 foot sheet is 32 square feet, so 2.44 times 32 gives 78.1 pounds. Mill tolerance moves a real sheet a pound or two either way. **Why do some charts give a slightly heavier weight per square foot?** Because they use the gauge standard constant rather than the density of steel. The Manufacturers Standard Gauge scale is built on 41.82 pounds per square foot per inch, a figure inherited from wrought iron. Modern mild steel is 0.2836 pounds per cubic inch, which works out at 40.84. The gap is about 2.4 percent, so 16 gauge comes out at 2.50 pounds per square foot on the gauge constant and 2.44 on the real density. This page uses the real density, because the question people are asking is what the sheet will actually weigh. **How do I work out the weight of any steel sheet?** Multiply thickness in inches by 40.84 to get pounds per square foot, then multiply by the area in square feet. The 40.84 figure is the density of steel, 0.2836 pounds per cubic inch, times 144 square inches per square foot. --- ## About Gauge Charts Canonical: https://gaugecharts.com/about Gauge Charts is a free browser version of shop and trade reference data, built and maintained by John Weeks, a web developer. There is no sign-up, no download and no paywall. The game loads and you play, and the rules and strategy pages are written by hand rather than generated. ### Who runs Gauge Charts This site is built and run by John Weeks, a web developer who designs, codes and maintains every game in the network himself. I am a web developer. I build for the web full time, mostly TypeScript and PHP on the server, React and Tailwind CSS on the front end, and I build and run my own sites rather than only shipping other people's. This network came out of a simple frustration: most free online versions of classic games are slow, buried under adverts, gated behind an account, or built once and abandoned. I wanted the version I would actually want to play (instant, playable on a phone, no sign-up, and accurate to the real rules), and then to write down properly how the game works so anyone can learn it in one page. Every site here is a single game on its own domain. I write the code, the rules, the strategy and the reference tables myself, and I keep them current. There is no content farm behind this and no AI-generated filler: if a page states an odds figure or a scoring rule, it came from a solver I wrote or a primary source I can point you at. ### What this site is trying to be The goal is simple: the best free version of shop and trade reference data on the web, and the clearest explanation of how it works. - Playable in about a second, on a phone, in portrait, with no account. - Accurate to the real rules, including the variants people actually play. - Explained properly: rules, scoring and strategy written out, not padded. - Kept working. A game that breaks in a browser update gets fixed. ### How the site is paid for, and what it knows about you Adverts pay the hosting and the time. Being straight about that, and about the data side, matters more than pretending the site runs on goodwill. The site is free and always will be. Display advertising is what will pay for it, and the slots go around the play area rather than over it. An advert will never cover the game or interrupt you mid-turn. Your game statistics (streaks, best scores, preferences) are stored in your own browser using localStorage. They are not sent to me, there is no account, and clearing your browser data clears them permanently. Analytics tell me which pages are useful. Advertising has not started yet, and when it does the advertising partners will set their own cookies. The privacy page lists what is collected either way, and how to opt out of it. ### Corrections and contact The fastest way to reach me is email: john.weeks.dev@gmail.com. I read everything sent there. **Who created Gauge Charts?** John Weeks, a web developer, built and maintains it. The code, the game logic and the written rules and strategy are all his own work. **Is Gauge Charts free?** Yes, completely. There is no account, no download, no trial and no paid tier. Display advertising covers the costs. **Do I need to create an account or install anything?** No. The game runs in your browser. Your scores and preferences are saved on your own device, so nothing needs to be signed into. **Can I use the rules, tables or score sheets on my own site?** Yes, with attribution and a link back. The reference data is published for reuse. That is the point of writing it out properly. **I found a mistake in the rules. What should I do?** Email john.weeks.dev@gmail.com and say what is wrong. Rule variations differ by region and household, so specifics help, and genuine corrections get made. --- ## Privacy Policy Canonical: https://gaugecharts.com/privacy Gauge Charts has no accounts and no server-side database, so it collects no personal information directly. Your game progress is stored in your own browser and never sent anywhere. This page sets out the analytics and advertising technologies the site does use, what they collect, and how to opt out. ### The short version If you read nothing else on this page, this is the substance of it. - There is no account, no login and no sign-up form. Nothing is submitted to us. - Your scores, streaks and settings are saved in your own browser and stay on your device. - The site is free because it shows adverts. Advertising and analytics partners set cookies. - Advertising has not started on this site yet. When it does, visitors in the UK, EEA and Switzerland will be asked for consent before any advertising cookie is set, and will be able to change that answer at any time. - We do not sell personal information, and we have nothing to sell. We hold no database of visitors. ### What is stored in your browser Game data is kept locally with the browser’s localStorage. It is not personal information and we cannot read it. Your best scores, games played, streaks and preferences are saved in your own browser using localStorage. This is a storage area belonging to your device, not to us: the data is never transmitted, we have no way to request it, and it is not linked to any identifier. Clearing your browser data, or using private browsing, removes it permanently. There is no backup and no recovery, which is the trade for not asking you to create an account. ### Analytics Aggregate measurement only: how many people came, and which pages were useful. The site uses Google Analytics to understand overall traffic: how many visits there were, which pages were read, roughly where in the world visitors were, and whether the pages loaded quickly. It reports in aggregate and is not used to identify you. Our hosting provider also records standard request information at the network edge: the page requested, the response status, the browser type and the country. This is the equivalent of a web server log, it is what tells us which search and AI crawlers are reading the site, and it contains no name, email or account. ### Advertising Adverts pay for the hosting and the time. This is exactly what they do and do not do. No adverts run on this site today. The plan is to fund it with display advertising through Google AdSense, and the honest version of this section describes what that will mean rather than pretending it is already happening. Google and its advertising partners may then use cookies or similar technologies to serve adverts, to measure whether an advert was seen and, where you have consented, to choose adverts based on your previous visits to this and other sites. Adverts are placed around the game, never over it, and never interrupt a turn. That is a design rule, not a promise we can quietly drop: an advert covering the play area would make the site worse at the one thing it exists to do. You can opt out of personalised Google advertising at any time through Google’s Ads Settings. Blocking or deleting cookies in your browser settings works too, and the game will keep running normally if you do. ### Consent, and how to change your mind What is set today, and what changes on the day advertising starts. Right now the only non-essential cookies here belong to analytics, and there is no advertising and no consent notice. On the day adverts are switched on, visitors in the United Kingdom, the European Economic Area and Switzerland will get a consent notice before any advertising cookie is set. It records your choices and can be reopened whenever you want to change them, so you are never locked into a single decision. Essential storage, the localStorage your game progress lives in, is not covered by that notice, because the site cannot function as a game without it and it never leaves your device. ### Your rights over your data Under the UK GDPR, the EU GDPR and similar laws you have rights over personal data held about you, and the honest answer here is that we hold almost none. We hold no account records, no email list and no profile of you. There is nothing on our side to export, correct or delete, because there is no database of visitors to hold it in. Where personal data is processed, it is processed by the third parties named above (Google Analytics and the advertising partners) under their own privacy policies. Requests about that data are best made to them directly, and their policies set out how. Google’s covers both its analytics and its advertising products. If you have a privacy question, or you believe something on this site is handling data incorrectly, email john.weeks.dev@gmail.com and it will be looked at properly. ### Children This is a general-audience site, not a service directed at children. The games here are traditional family games and people of all ages play them, but the site is not directed at children under 13 and we do not knowingly collect personal information from them. Since there are no accounts and no forms, there is no route by which a child could submit personal information to us in the first place. If you believe a child has somehow provided personal information through this site, contact us and we will act on it. ### External links and changes to this policy Pages here sometimes link to other sites: rule references, source material, and the other games in this network. Those sites have their own privacy policies and this one does not cover them. If this policy changes materially, the date below changes with it. Substantive changes are made to the page itself rather than announced and forgotten. **Do you sell my personal information?** No. We hold no database of visitors, so there is nothing to sell. Advertising partners operate under their own policies, and you can withdraw consent for them at any time. **Do I have to accept cookies to play?** No. Declining non-essential cookies does not affect the game. Your progress is saved in your own browser either way, and that storage never leaves your device. **How do I delete the data this site has about me?** Clear your browser data and it is gone. That is genuinely all of it on our side. There is no account to close and no record held on a server. --- ## Terms of Use Canonical: https://gaugecharts.com/terms Gauge Charts is free to use, with no account and no subscription. These terms cover what you can do with the site and what it does and does not promise. They are meant to be read, so they are written in plain English. ### Using the site Play as much as you like. There is no account to breach and no quota to exceed. You may use this site for personal, non-commercial enjoyment, and you may link to any page on it freely. No permission is needed to link, embed a link, or recommend the site. What you may not do is the obvious short list: interfere with the site or its security, attempt to disrupt it for other people, scrape it at a volume that degrades it for others, or represent it as your own. ### Reusing the rules, tables and score sheets The reference material is published so it can be reused. Attribution is the only condition. The reference data on this site (scoring charts, odds tables, printable score sheets and the computed figures behind them) is published under a Creative Commons Attribution licence. You may copy it, reprint it, teach from it and build on it, including commercially, provided you credit Gauge Charts and link back to the page you took it from. That is a deliberate choice, not an oversight. This material was produced so people could use it; a table nobody is allowed to quote is a table that helps nobody. The site’s own software, layout, graphics and branding are not covered by that licence and remain the property of the site owner. ### Independence and trademarks shop and trade reference data is a traditional game. This site is independent and is not affiliated with, endorsed by or connected to any commercial publisher. shop and trade reference data is played in many households and regions with local variations, and this site documents it as the traditional game it is. Where a name is also used commercially by a company, it is used here descriptively, to say which game the page is about. No affiliation, sponsorship or endorsement is claimed or implied. All trademarks referenced remain the property of their respective owners. ### What this site does not promise It is a free game, offered as it is. The site is provided "as is", without warranty of any kind. It may occasionally be unavailable, a browser update may break something, and rule variations differ between regions and households, so the rules described here may not match the version played at your kitchen table. Nothing here is legal, financial or professional advice, and the site is not liable for any loss arising from its use to the extent the law allows. If you find a mistake, the useful response is to tell us so it can be corrected, and corrections are made. ### Changes and contact These terms may be updated; the date below changes when they are. Questions go to john.weeks.dev@gmail.com. **Can I print the score sheets for my games night?** Yes, that is exactly what they are for. Print as many as you like, for home, school or a club. **Can I use the odds tables in a book, video or article?** Yes, including commercially, as long as you credit Gauge Charts and link to the page you took the figures from. **Can I copy the site itself?** No. The reference data is openly licensed; the software, design and branding are not. --- ## Contact Canonical: https://gaugecharts.com/contact Email is the way to reach a real person here: **john.weeks.dev@gmail.com**. John Weeks builds and maintains the site and reads everything sent to that address. There is no contact form, no ticket queue and no support bot. ### What to write about A one-line subject that names the page or the topic gets a faster and more useful answer. - **Rule corrections.** The most valuable reason to write. shop and trade reference data varies by region and household, so say which rule, which page, and how you play it. Specifics get acted on. - **A bug in the game.** Tell us the browser and what happened. A game that breaks in a browser update gets fixed. - **Reusing the data.** The score sheets, tables and odds are licensed for reuse with attribution. Write if you want to check how to credit it, or need a cut of the data we have not published. - **Privacy questions or requests.** See the privacy policy first. The short answer is that there is no account and no database. Write if anything is unclear. - **Press and research.** Happy to help with quotes, figures or background on the game and how the numbers were produced. ### Who you are emailing This site is built and run by John Weeks, a web developer who designs, codes and maintains every game in the network himself. John Weeks is a web developer who writes the code, the rules and the strategy content on every site in this network. There is no editorial team behind the address and no agency. Messages go to the person who can actually change the page. Replies usually come within a few days. Corrections are prioritised over everything else, because a wrong rule on a reference page is the one problem that makes the whole site less useful. **Is there a contact form?** No. These are static pages with no server behind them, so a form would have nowhere to submit to without adding a third-party service that collects more data than the rest of the site does. Email is simpler and more private. **How quickly will I get a reply?** Usually within a few days. Rule corrections and bug reports get looked at first. **I think a rule on this site is wrong. What should I include?** The page, the specific rule, and how you play it, including where you play it, since regional variants are usually the explanation. If it checks out, the page is updated and credited.