Every standard building-wire size from 14 AWG to 500 kcmil — physical dimensions, NEC Chapter 9 Table 8 resistance in both Ω/kft and Ω/km, and Table 310.16 ampacity at 75 °C.
| Size | Dia mm | mm² | Circular Mils | Ω/kft Cu | Ω/km Cu | Ω/kft Al | Ω/km Al | Amp 75°C Cu | Amp 75°C Al |
|---|---|---|---|---|---|---|---|---|---|
| 14 AWG | 1.63 | 2.1 | 4,110 | 3.07 | 10.072 | 5.06 | 16.601 | 20 | — |
| 12 AWG | 2.05 | 3.3 | 6,530 | 1.93 | 6.332 | 3.18 | 10.433 | 25 | 20 |
| 10 AWG | 2.59 | 5.3 | 10,380 | 1.21 | 3.970 | 2 | 6.562 | 35 | 30 |
| 8 AWG | 3.26 | 8.4 | 16,510 | 0.764 | 2.507 | 1.26 | 4.134 | 50 | 40 |
| 6 AWG | 4.11 | 13.3 | 26,240 | 0.491 | 1.611 | 0.808 | 2.651 | 65 | 50 |
| 4 AWG | 5.19 | 21.1 | 41,740 | 0.308 | 1.010 | 0.508 | 1.667 | 85 | 65 |
| 3 AWG | 5.83 | 26.7 | 52,620 | 0.245 | 0.804 | 0.403 | 1.322 | 100 | 75 |
| 2 AWG | 6.54 | 33.6 | 66,360 | 0.194 | 0.636 | 0.319 | 1.047 | 115 | 90 |
| 1 AWG | 7.35 | 42.4 | 83,690 | 0.154 | 0.505 | 0.253 | 0.830 | 130 | 100 |
| 1/0 AWG | 8.25 | 53.5 | 105,600 | 0.122 | 0.400 | 0.201 | 0.659 | 150 | 120 |
| 2/0 AWG | 9.27 | 67.4 | 133,100 | 0.0967 | 0.317 | 0.159 | 0.522 | 175 | 135 |
| 3/0 AWG | 10.40 | 85.0 | 167,800 | 0.0766 | 0.251 | 0.126 | 0.413 | 200 | 155 |
| 4/0 AWG | 11.68 | 107.2 | 211,600 | 0.0608 | 0.199 | 0.1 | 0.328 | 230 | 180 |
| 250 kcmil | 12.70 | 126.7 | 250,000 | 0.0515 | 0.169 | 0.0847 | 0.278 | 255 | 205 |
| 300 kcmil | 13.91 | 152.0 | 300,000 | 0.0429 | 0.141 | 0.0707 | 0.232 | 285 | 230 |
| 350 kcmil | 15.03 | 177.3 | 350,000 | 0.0367 | 0.120 | 0.0605 | 0.198 | 310 | 250 |
| 400 kcmil | 16.06 | 202.7 | 400,000 | 0.0321 | 0.105 | 0.0529 | 0.174 | 335 | 270 |
| 500 kcmil | 17.96 | 253.3 | 500,000 | 0.0258 | 0.085 | 0.0424 | 0.139 | 380 | 310 |
Each three-step move up the AWG ladder halves the resistance, and each step changes area by about 26%. Metric resistance is the same data × 3.281 ft/m. Values are DC resistance for uncoated conductors at 75 °C; ampacities assume ≤3 current-carrying conductors at 30 °C — use the ampacity calculator for derated conditions, and see the annotated Table 8 for the fine print.
Thousands of circular mils — the cross-sectional area unit used above 4/0 AWG. One circular mil is the area of a circle one mil (0.001 in) in diameter.