How to read the chart
The chart is in two parts. The first gives each conductor’s physical data: its area in circular mils and square millimetres, its bare diameter, its dc resistance and the nearest metric size. The second gives the ampacity the NEC assigns to the size in copper and in aluminum, the largest breaker that protects a copper conductor at its 75 °C rating, the largest dwelling service it can serve by the 83 % rule, and what the size is typically used for. The sizes run from the smallest to the largest, so the gauge numbers count down: 18 AWG first, then 16, 14 and so on to 1 AWG, then 1/0 (one-aught) to 4/0 (four-aught), then kcmil.
Ampacity comes in three columns because insulation comes in three temperature ratings. Use the column your conductor and its terminals can both take; for most breakers and panels that is 75 °C, and for circuits of 100 A or less with unmarked equipment it is 60 °C. Then correct for a hot location or a crowded raceway. The ampacity calculator does both.
Size, area, diameter and resistance
| Size | Area (cmil) | Area (mm²) | Diameter, solid (in) | Diameter, stranded (in) | Stranded (mm) | Copper Ω/1000 ft | Aluminum Ω/1000 ft | Copper Ω/km | Nearest metric |
|---|---|---|---|---|---|---|---|---|---|
| 18 AWG | 1,620 | 0.823 | 0.04 | 0.046 | 1.17 | 7.95 | 13.1 | 26.1 | 0.75 mm² (−9 %) |
| 16 AWG | 2,580 | 1.31 | 0.051 | 0.058 | 1.47 | 4.99 | 8.21 | 16.4 | 1.5 mm² (+15 %) |
| 14 AWG | 4,110 | 2.08 | 0.064 | 0.073 | 1.85 | 3.14 | 5.17 | 10.3 | 2.5 mm² (+20 %) |
| 12 AWG | 6,530 | 3.31 | 0.081 | 0.092 | 2.34 | 1.98 | 3.25 | 6.5 | 4 mm² (+21 %) |
| 10 AWG | 10,380 | 5.261 | 0.102 | 0.116 | 2.95 | 1.24 | 2.04 | 4.07 | 6 mm² (+14 %) |
| 8 AWG | 16,510 | 8.367 | 0.128 | 0.146 | 3.71 | 0.778 | 1.28 | 2.55 | 10 mm² (+20 %) |
| 6 AWG | 26,240 | 13.3 | — | 0.184 | 4.67 | 0.491 | 0.808 | 1.61 | 16 mm² (+20 %) |
| 4 AWG | 41,740 | 21.15 | — | 0.232 | 5.89 | 0.308 | 0.508 | 1.01 | 25 mm² (+18 %) |
| 3 AWG | 52,620 | 26.67 | — | 0.26 | 6.60 | 0.245 | 0.403 | 0.804 | 25 mm² (−6 %) |
| 2 AWG | 66,360 | 33.62 | — | 0.292 | 7.42 | 0.194 | 0.319 | 0.636 | 35 mm² (+4 %) |
| 1 AWG | 83,690 | 42.41 | — | 0.332 | 8.43 | 0.154 | 0.253 | 0.505 | 50 mm² (+18 %) |
| 1/0 AWG | 105,600 | 53.49 | — | 0.372 | 9.45 | 0.122 | 0.201 | 0.4 | 50 mm² (−7 %) |
| 2/0 AWG | 133,100 | 67.43 | — | 0.418 | 10.62 | 0.0967 | 0.159 | 0.317 | 70 mm² (+4 %) |
| 3/0 AWG | 167,800 | 85.01 | — | 0.47 | 11.94 | 0.0766 | 0.126 | 0.251 | 95 mm² (+12 %) |
| 4/0 AWG | 211,600 | 107.2 | — | 0.528 | 13.41 | 0.0608 | 0.1 | 0.199 | 120 mm² (+12 %) |
| 250 kcmil | 250,000 | 127 | — | 0.575 | 14.60 | 0.0515 | 0.0847 | 0.169 | 120 mm² (−6 %) |
| 300 kcmil | 300,000 | 152 | — | 0.63 | 16.00 | 0.0429 | 0.0707 | 0.141 | 150 mm² (−1 %) |
| 350 kcmil | 350,000 | 177 | — | 0.681 | 17.30 | 0.0367 | 0.0605 | 0.12 | 185 mm² (+5 %) |
| 400 kcmil | 400,000 | 203 | — | 0.728 | 18.49 | 0.0321 | 0.0529 | 0.105 | 185 mm² (−9 %) |
| 500 kcmil | 500,000 | 253 | — | 0.813 | 20.65 | 0.0258 | 0.0424 | 0.0846 | 240 mm² (−5 %) |
| 600 kcmil | 600,000 | 304 | — | 0.893 | 22.68 | 0.0214 | 0.0353 | 0.0702 | 300 mm² (−1 %) |
| 700 kcmil | 700,000 | 355 | — | 0.964 | 24.49 | 0.0184 | 0.0303 | 0.0604 | 400 mm² (+13 %) |
| 750 kcmil | 750,000 | 380 | — | 0.998 | 25.35 | 0.0171 | 0.0282 | 0.0561 | 400 mm² (+5 %) |
| 800 kcmil | 800,000 | 405 | — | 1.03 | 26.16 | 0.0161 | 0.0265 | 0.0528 | 400 mm² (−1 %) |
| 900 kcmil | 900,000 | 456 | — | 1.094 | 27.79 | 0.0143 | 0.0235 | 0.0469 | 500 mm² (+10 %) |
| 1000 kcmil | 1,000,000 | 507 | — | 1.152 | 29.26 | 0.0129 | 0.0212 | 0.0423 | 500 mm² (−1 %) |
| 1250 kcmil | 1,250,000 | 633 | — | 1.289 | 32.74 | 0.0103 | 0.0169 | 0.0338 | 630 mm² (−0 %) |
| 1500 kcmil | 1,500,000 | 760 | — | 1.412 | 35.86 | 0.00858 | 0.0141 | 0.0281 | 800 mm² (+5 %) |
| 1750 kcmil | 1,750,000 | 887 | — | 1.526 | 38.76 | 0.00735 | 0.0121 | 0.0241 | 800 mm² (−10 %) |
| 2000 kcmil | 2,000,000 | 1013 | — | 1.632 | 41.45 | 0.00643 | 0.0106 | 0.0211 | 1,000 mm² (−1 %) |
Sizes from 18 to 8 AWG are made solid as well as stranded, and the two have the same area but different diameters: the stranded conductor is wider because round strands leave gaps between them. Compact stranding is about 9 % smaller across than the Class B stranding shown here.
Ampacity chart for copper and aluminum
| Size | Copper | Aluminum or CCA | Largest breaker, copper at 75 °C | Dwelling service, Cu / Al (310.12) | Typical uses | ||||
|---|---|---|---|---|---|---|---|---|---|
| 60 °C | 75 °C | 90 °C | 60 °C | 75 °C | 90 °C | ||||
| 18 AWG | — | — | 14 | — | — | — | 7 A | — | Fixture wire, doorbell, thermostat and control wiring |
| 16 AWG | — | — | 18 | — | — | — | 10 A | — | Fixture wire, cords and control wiring; 10 A lighting circuits from 2026 |
| 14 AWG | 15 | 20 | 25 | — | — | — | 15 A | — | Lighting and general-purpose receptacle circuits |
| 12 AWG | 20 | 25 | 30 | 15 | 20 | 25 | 20 A | — | Kitchen, bathroom, laundry and garage receptacle circuits |
| 10 AWG | 30 | 35 | 40 | 25 | 30 | 35 | 30 A | — | Dryers, water heaters, smaller air conditioners |
| 8 AWG | 40 | 50 | 55 | 35 | 40 | 45 | 50 A | — | Wall ovens, cooktops, smaller ranges |
| 6 AWG | 55 | 65 | 75 | 40 | 50 | 55 | 70 A | — | Ranges, EV chargers, small subpanels |
| 4 AWG | 70 | 85 | 95 | 55 | 65 | 75 | 90 A | 100 A / — | Subpanel feeders and smaller services |
| 3 AWG | 85 | 100 | 115 | 65 | 75 | 85 | 100 A | 110 A / — | Feeders and smaller services |
| 2 AWG | 95 | 115 | 130 | 75 | 90 | 100 | 125 A | 125 A / 100 A | Feeders; aluminum dwelling services |
| 1 AWG | 110 | 130 | 145 | 85 | 100 | 115 | 150 A | 150 A / 110 A | Feeders and dwelling services |
| 1/0 AWG | 125 | 150 | 170 | 100 | 120 | 135 | 150 A | 175 A / 125 A | Dwelling services and feeders |
| 2/0 AWG | 145 | 175 | 195 | 115 | 135 | 150 | 175 A | 200 A / 150 A | Dwelling services and feeders |
| 3/0 AWG | 165 | 200 | 225 | 130 | 155 | 175 | 200 A | 225 A / 175 A | Dwelling services and feeders |
| 4/0 AWG | 195 | 230 | 260 | 150 | 180 | 205 | 250 A | 250 A / 200 A | Dwelling services and feeders |
| 250 kcmil | 215 | 255 | 290 | 170 | 205 | 230 | 300 A | 300 A / 225 A | Larger services and commercial feeders |
| 300 kcmil | 240 | 285 | 320 | 195 | 230 | 260 | 300 A | 300 A / 250 A | Larger services and commercial feeders |
| 350 kcmil | 260 | 310 | 350 | 210 | 250 | 280 | 350 A | 350 A / 300 A | Larger services and commercial feeders |
| 400 kcmil | 280 | 335 | 380 | 225 | 270 | 305 | 350 A | 400 A / 300 A | Larger services and commercial feeders |
| 500 kcmil | 320 | 380 | 430 | 260 | 310 | 350 | 400 A | 400 A / 350 A | Larger services and commercial feeders |
| 600 kcmil | 350 | 420 | 475 | 285 | 340 | 385 | 450 A | 400 A / 400 A | Commercial services and feeders, often in parallel sets |
| 700 kcmil | 385 | 460 | 520 | 315 | 375 | 425 | 500 A | 400 A / 400 A | Commercial services and feeders, often in parallel sets |
| 750 kcmil | 400 | 475 | 535 | 320 | 385 | 435 | 500 A | 400 A / 400 A | Commercial services and feeders, often in parallel sets |
| 800 kcmil | 410 | 490 | 555 | 330 | 395 | 445 | 500 A | 400 A / 400 A | Commercial services and feeders, often in parallel sets |
| 900 kcmil | 435 | 520 | 585 | 355 | 425 | 480 | 600 A | 400 A / 400 A | Commercial services and feeders, often in parallel sets |
| 1000 kcmil | 455 | 545 | 615 | 375 | 445 | 500 | 600 A | 400 A / 400 A | Commercial services and feeders, often in parallel sets |
| 1250 kcmil | 495 | 590 | 665 | 405 | 485 | 545 | 600 A | 400 A / 400 A | Commercial services and feeders, often in parallel sets |
| 1500 kcmil | 525 | 625 | 705 | 435 | 520 | 585 | 700 A | 400 A / 400 A | Commercial services and feeders, often in parallel sets |
| 1750 kcmil | 545 | 650 | 735 | 455 | 545 | 615 | 700 A | 400 A / 400 A | Commercial services and feeders, often in parallel sets |
| 2000 kcmil | 555 | 665 | 750 | 470 | 560 | 630 | 700 A | 400 A / 400 A | Commercial services and feeders, often in parallel sets |
A dash means the table lists no value: aluminum is not used below 12 AWG, and 18 and 16 AWG copper appear only in the 90 °C column, for special uses. The 2026 NEC adds 16 AWG copper at 10 A in the 60 °C column and 14 AWG copper-clad aluminum at 10 A, deletes the 18 AWG row, and keeps the 18 and 16 AWG 90 °C values only for Types MI and MTW. Those 2026 changes come from a single NFPA draft that we have not yet checked against the printed book, so the chart shows the 2023 values and our calculators warn whenever a 2026 result depends on them.
Every size to scale
Reading the typical-uses column
The uses column describes where each size usually turns up in buildings, not what a particular circuit needs. Two things move a real circuit away from the typical size. Conditions of use can push it up: a hot attic, a crowded conduit, a sunny roof or a long run all call for a larger conductor than the chart’s first match. Specific articles can push it down or sideways: motor and air-conditioning circuits are protected by breakers much larger than the wire’s ampacity, because the motor rules provide overload protection separately. The breaker column applies the general rule only, with the next-size-up allowance of 240.4(B) and the small-conductor limits of 240.4(D).
Solid or stranded
Solid conductors are cheaper, hold their shape under a terminal screw and are the norm in 14 to 10 AWG building cable. Stranded conductors bend more easily, survive vibration and pull far better through conduit, which is why larger building wire is almost always stranded: conductors 8 AWG and larger installed in raceways must be stranded unless another rule allows solid (310.3(C) in the 2020 and 2023 editions). Stranding does not change the ampacity, and the two constructions have the same nominal area. It does change the diameter, and slightly the resistance: 12 AWG solid copper is 1.93 Ω per 1000 ft and 7-strand 12 AWG is 1.98 Ω, because each strand is twisted and slightly longer than the cable.
Insulation and the overall diameter
The diameters here are for the bare metal. The finished wire is larger by twice the insulation thickness, which depends on the type: THHN’s thin nylon-jacketed insulation adds the least, while XHHW, RHW and USE add more. That difference is what decides how many conductors fit in a conduit, so raceway fill uses the insulated diameters of Chapter 9, Table 5 rather than this chart. For bare conductors, such as a bare equipment grounding conductor in a raceway, the 2026 edition says plainly that the Table 8 dimensions apply.
How the AWG sizes work
American Wire Gauge is a geometric series. It fixes 36 AWG at 0.005 in. and 4/0 at 0.46 in., a ratio of 92, and spaces 39 gauges between them, so each gauge is 1.1229 times the diameter of the next smaller one and 1.261 times its area. That gives the rules of thumb electricians use:
- Three gauges double the area: 3 AWG has 2.01 times the area of 6 AWG.
- Six gauges double the diameter and quadruple the area: 4 AWG has 4.02 times the area of 10 AWG.
- Ten gauges multiply the area by about ten: 4 AWG has 10.2 times the area of 14 AWG.
Because resistance falls in proportion to area, the same rules apply to resistance in reverse: going up three sizes roughly halves the voltage drop. Past 4/0 the gauge numbers run out, and conductors are named by area directly: 250, 300, 350 kcmil and up, in thousands of circular mils. Electricians often write the older “MCM” for the same thing.
Circular mils and square millimetres
A circular mil is the area of a circle one mil (a thousandth of an inch) in diameter. It makes the arithmetic of round wire easy: a solid conductor d mils across has an area of d² circular mils, with no π to carry. 10 AWG solid is 102 mils across and 10,380 cmil. To convert, 1 mm² = 1,973.5 cmil, so divide circular mils by 1,973.5 for square millimetres. The NEC’s own tables use circular mils for voltage-drop and grounding calculations, which is why the proportional grounding-conductor rule and the K-factor voltage drop formula both work in cmil.
Resistance and voltage drop
The resistance column is the Chapter 9 value at 75 °C, the temperature the NEC assumes for voltage-drop work. Copper and aluminum both get about 0.32 % more resistive per degree of temperature rise, so a lightly loaded conductor running cooler drops a little less than the table suggests. Multiply the resistance by twice the one-way length for a two-wire circuit, or use the voltage drop calculator, which also handles three-phase circuits, ac reactance from Chapter 9, Table 9, and the IEC and BS 7671 methods.
Using the ampacity columns safely
The ampacity chart is a starting point, not the answer for a circuit. Table 310.16 assumes a 30 °C (86 °F) ambient and no more than three current-carrying conductors in the raceway or cable; correct for anything hotter or more crowded. Size the circuit for 125 % of any continuous load, check that the terminals allow the column you used, and remember that 14, 12 and 10 AWG are capped at 15, 20 and 30 A by 240.4(D) in copper. A dwelling service may use the 83 % rule of 310.12, which is what the dwelling column shows. The wire size calculator applies all of these rules, edition by edition, and the ground wire size calculator sizes the equipment grounding conductor that goes with it.
Metric equivalents
Metric cables follow IEC 60228, a separate series of nominal areas: 1.5, 2.5, 4, 6, 10, 16 mm² and so on. No AWG size matches one exactly. 14 AWG (2.08 mm²) sits between 1.5 and 2.5 mm², and 12 AWG (3.31 mm²) sits 17 % below 4 mm². The chart lists the nearest size by area ratio, with the difference in brackets. Treat it as a guide to what a metric equivalent looks like, not as a substitution rule: a metric cable is sized from its own current-carrying capacity tables (IEC 60364-5-52 or BS 7671 Appendix 4) for its installation method.
Look up a size under your conditions
Choose a size, insulation, ambient temperature and number of conductors to see the usable ampacity and the largest breaker for your installation: