Maximum one-way run in feet for copper conductors at a 3% drop. Cells are blank where the size fails the 75 °C ampacity for that load.
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| Copper size \ Amps | 15 A | 20 A | 30 A | 40 A | 50 A | 60 A | 80 A | 100 A |
|---|---|---|---|---|---|---|---|---|
| 14 AWG | 39 | 29 | — | — | — | — | — | — |
| 12 AWG | 62 | 47 | — | — | — | — | — | — |
| 10 AWG | 99 | 74 | 50 | — | — | — | — | — |
| 8 AWG | 157 | 118 | 79 | 59 | 47 | — | — | — |
| 6 AWG | 244 | 183 | 122 | 92 | 73 | 61 | — | — |
| 4 AWG | 390 | 292 | 195 | 146 | 117 | 97 | 73 | — |
| 3 AWG | 490 | 367 | 245 | 184 | 147 | 122 | 92 | 73 |
| 2 AWG | 619 | 464 | 309 | 232 | 186 | 155 | 116 | 93 |
| 1 AWG | 779 | 584 | 390 | 292 | 234 | 195 | 146 | 117 |
| 1/0 AWG | 984 | 738 | 492 | 369 | 295 | 246 | 184 | 148 |
| 2/0 AWG | 1241 | 931 | 620 | 465 | 372 | 310 | 233 | 186 |
| 3/0 AWG | 1567 | 1175 | 783 | 587 | 470 | 392 | 294 | 235 |
| 4/0 AWG | 1974 | 1480 | 987 | 740 | 592 | 493 | 370 | 296 |
Doubling the voltage doubles every distance — one reason 240 V is the right choice for long runs to outbuildings, EV chargers and pumps.
| Copper size \ Amps | 15 A | 20 A | 30 A | 40 A | 50 A | 60 A | 80 A | 100 A |
|---|---|---|---|---|---|---|---|---|
| 14 AWG | 78 | 59 | — | — | — | — | — | — |
| 12 AWG | 124 | 93 | — | — | — | — | — | — |
| 10 AWG | 198 | 149 | 99 | — | — | — | — | — |
| 8 AWG | 314 | 236 | 157 | 118 | 94 | — | — | — |
| 6 AWG | 489 | 367 | 244 | 183 | 147 | 122 | — | — |
| 4 AWG | 779 | 584 | 390 | 292 | 234 | 195 | 146 | — |
| 3 AWG | 980 | 735 | 490 | 367 | 294 | 245 | 184 | 147 |
| 2 AWG | 1237 | 928 | 619 | 464 | 371 | 309 | 232 | 186 |
| 1 AWG | 1558 | 1169 | 779 | 584 | 468 | 390 | 292 | 234 |
| 1/0 AWG | 1967 | 1475 | 984 | 738 | 590 | 492 | 369 | 295 |
| 2/0 AWG | 2482 | 1861 | 1241 | 931 | 745 | 620 | 465 | 372 |
| 3/0 AWG | 3133 | 2350 | 1567 | 1175 | 940 | 783 | 587 | 470 |
| 4/0 AWG | 3947 | 2961 | 1974 | 1480 | 1184 | 987 | 740 | 592 |
Computed from Vd = 2 × I × L × R/1000 with NEC Chapter 9 Table 8 resistance. For aluminum, metric lengths, power factor or parallel sets, use the full calculator.
Find your load current in the column headers and your wire size in the rows — the cell is the farthest one-way distance that stays within a 3% drop. For the 5% total budget, multiply by 1.67.