12 AWG wire is 2.053 mm across with a 3.31 mm² cross-section; 14 AWG is 1.628 mm. In homes, 14 AWG copper is protected at 15 A and 12 AWG at 20 A.
| AWG | Diameter (mm) | Diameter (in) | Area (mm²) | Amps 60 °C | Amps 75 °C | Amps 90 °C |
|---|---|---|---|---|---|---|
| 4/0 | 11.684 | 0.4600 | 107.219 | 195 | 230 | 260 |
| 3/0 | 10.405 | 0.4096 | 85.029 | 165 | 200 | 225 |
| 2/0 | 9.266 | 0.3648 | 67.431 | 145 | 175 | 195 |
| 1/0 | 8.251 | 0.3249 | 53.475 | 125 | 150 | 170 |
| 1 | 7.348 | 0.2893 | 42.408 | 110 | 130 | 145 |
| 2 | 6.544 | 0.2576 | 33.631 | 95 | 115 | 130 |
| 3 | 5.827 | 0.2294 | 26.670 | 85 | 100 | 115 |
| 4 | 5.189 | 0.2043 | 21.151 | 70 | 85 | 95 |
| 5 | 4.621 | 0.1819 | 16.773 | — | — | — |
| 6 | 4.115 | 0.1620 | 13.302 | 55 | 65 | 75 |
| 7 | 3.665 | 0.1443 | 10.549 | — | — | — |
| 8 | 3.264 | 0.1285 | 8.366 | 40 | 50 | 55 |
| 9 | 2.906 | 0.1144 | 6.634 | — | — | — |
| 10 | 2.588 | 0.1019 | 5.261 | 30 | 35 | 40 |
| 11 | 2.305 | 0.0907 | 4.172 | — | — | — |
| 12 | 2.053 | 0.0808 | 3.309 | 20 | 25 | 30 |
| 13 | 1.828 | 0.0720 | 2.624 | — | — | — |
| 14 | 1.628 | 0.0641 | 2.081 | 15 | 20 | 25 |
| 15 | 1.450 | 0.0571 | 1.650 | — | — | — |
| 16 | 1.291 | 0.0508 | 1.309 | — | — | — |
| 17 | 1.150 | 0.0453 | 1.038 | — | — | — |
| 18 | 1.024 | 0.0403 | 0.823 | — | — | — |
| 19 | 0.912 | 0.0359 | 0.653 | — | — | — |
| 20 | 0.812 | 0.0320 | 0.518 | — | — | — |
| 21 | 0.723 | 0.0285 | 0.410 | — | — | — |
| 22 | 0.644 | 0.0253 | 0.326 | — | — | — |
| 23 | 0.573 | 0.0226 | 0.258 | — | — | — |
| 24 | 0.511 | 0.0201 | 0.205 | — | — | — |
| 26 | 0.405 | 0.0159 | 0.129 | — | — | — |
| 28 | 0.321 | 0.0126 | 0.081 | — | — | — |
| 30 | 0.255 | 0.0100 | 0.051 | — | — | — |
| 32 | 0.202 | 0.0080 | 0.032 | — | — | — |
| 34 | 0.160 | 0.0063 | 0.020 | — | — | — |
| 36 | 0.127 | 0.0050 | 0.013 | — | — | — |
| 38 | 0.101 | 0.0040 | 0.008 | — | — | — |
| 40 | 0.080 | 0.0031 | 0.005 | — | — | — |
How it is computed
Diameters come from the AWG definition: d = 0.127 mm × 92^((36 − n)/39), where 1/0 counts as 0, 2/0 as −1 and so on; area = π/4 × d². Ampacities are the copper values of NEC Table 310.16 for up to three current-carrying conductors at 30 °C ambient.
FAQ
Why does the table say 25 A for 12 AWG but breakers are 20 A?+
The NEC small-conductor rule (240.4(D)) caps overcurrent protection at 15 A for 14 AWG, 20 A for 12 AWG and 30 A for 10 AWG copper, below the table ampacity.
Which temperature column should I use?+
The lowest rating among the wire, the terminals and the device. Most residential breakers and receptacles are rated 60 °C or 75 °C, so the 90 °C column is mainly a starting point for derating.