Wire size chart
A 20 amp circuit needs 12 AWG copper, a 30 amp circuit 10 AWG and a 50 amp circuit 8 AWG copper with 75 °C terminations (6 AWG in NM-B cable). The chart lists every standard breaker from 15 to 400 amps.
| Breaker | Copper NM-B (60 °C) | Copper 75 °C | Aluminum 75 °C |
|---|---|---|---|
| 15 A | 14 AWG | 14 AWG | copper only |
| 20 A | 12 AWG | 12 AWG | copper only |
| 25 A | 10 AWG | 10 AWG | copper only |
| 30 A | 10 AWG | 10 AWG | copper only |
| 35 A | 8 AWG | 8 AWG | 8 AWG |
| 40 A | 8 AWG | 8 AWG | 8 AWG |
| 45 A | 6 AWG | 8 AWG | 6 AWG |
| 50 A | 6 AWG | 8 AWG | 6 AWG |
| 60 A | 4 AWG | 6 AWG | 4 AWG |
| 70 A | 4 AWG | 4 AWG | 3 AWG |
| 80 A | 3 AWG | 4 AWG | 2 AWG |
| 90 A | 2 AWG | 3 AWG | 2 AWG |
| 100 A | not made | 3 AWG | 1 AWG |
| 110 A | not made | 2 AWG | 1/0 AWG |
| 125 A | not made | 1 AWG | 2/0 AWG |
| 150 A | not made | 1/0 AWG | 3/0 AWG |
| 175 A | not made | 2/0 AWG | 4/0 AWG |
| 200 A | not made | 3/0 AWG | 250 kcmil |
| 225 A | not made | 4/0 AWG | 300 kcmil |
| 250 A | not made | 250 kcmil | 350 kcmil |
| 300 A | not made | 350 kcmil | 500 kcmil |
| 350 A | not made | 500 kcmil | — |
| 400 A | — | 600 kcmil | — |
- Copper NM-B (60 °C)
- Copper 75 °C
- Aluminum 75 °C
How the wire size chart is built
Each size is the smallest conductor whose ampacity, capped by the small-conductor limits, is at least the breaker rating. "Not made" in the NM-B column means NM-B cable is not sold in that size; use the 75 °C column for wire in conduit or SE/SER cable with 75 °C terminations. Aluminum is not used for circuits that need copper smaller than 8 AWG. A dash means no size up to 600 kcmil is enough.
Long runs need larger wire
The chart sizes for heat only. On a long run the voltage drop can call for a bigger wire; the wire size calculator checks both.