Guides / Shop charts · Updated
Wire gauge chart
From the NEC ampacity table, checked against wire makers' published copies. Your inspector has the final say.
Short answer
14 AWG copper goes on a 15 A breaker, 12 AWG on 20 A and 10 AWG on 30 A. 6 AWG copper is 50 A as NM-B cable or 60 A as THHN in conduit. Long runs need a bigger size for voltage drop.
Copper wire gauge chart
| AWG | 60 °C | 75 °C | 90 °C | Breaker, 60 °C | Breaker, 75 °C | Run at 240 V |
|---|---|---|---|---|---|---|
| 14 | 15 A | 20 A | 25 A | 15 A | 15 A | 76 ft |
| 12 | 20 A | 25 A | 30 A | 20 A | 20 A | 90 ft |
| 10 | 30 A | 35 A | 40 A | 30 A | 30 A | 96 ft |
| 8 | 40 A | 50 A | 55 A | 40 A | 50 A | 92 ft |
| 6 | 55 A | 65 A | 75 A | 50 A | 60 A | 122 ft |
| 4 | 70 A | 85 A | 95 A | 70 A | 80 A | 146 ft |
| 3 | 85 A | 100 A | 115 A | 80 A | 100 A | 146 ft |
| 2 | 95 A | 115 A | 130 A | 90 A | 110 A | 168 ft |
| 1 | 110 A | 130 A | 145 A | 110 A | 125 A | 187 ft |
| 1/0 | 125 A | 150 A | 170 A | 125 A | 150 A | 196 ft |
| 2/0 | 145 A | 175 A | 195 A | 125 A | 175 A | 212 ft |
| 3/0 | 165 A | 200 A | 225 A | 150 A | 200 A | 234 ft |
| 4/0 | 195 A | 230 A | 260 A | 175 A | 200 A | 296 ft |
Aluminum wire gauge chart
| AWG | 60 °C | 75 °C | 90 °C | Breaker, 60 °C | Breaker, 75 °C | Run at 240 V |
|---|---|---|---|---|---|---|
| 12 | 15 A | 20 A | 25 A | 15 A | 15 A | 73 ft |
| 10 | 25 A | 30 A | 35 A | 25 A | 25 A | 70 ft |
| 8 | 35 A | 40 A | 45 A | 35 A | 40 A | 70 ft |
| 6 | 40 A | 50 A | 55 A | 40 A | 50 A | 89 ft |
| 4 | 55 A | 65 A | 75 A | 50 A | 60 A | 118 ft |
| 3 | 65 A | 75 A | 85 A | 60 A | 70 A | 127 ft |
| 2 | 75 A | 90 A | 100 A | 70 A | 90 A | 125 ft |
| 1 | 85 A | 100 A | 115 A | 80 A | 100 A | 142 ft |
| 1/0 | 100 A | 120 A | 135 A | 100 A | 110 A | 162 ft |
| 2/0 | 115 A | 135 A | 150 A | 110 A | 125 A | 181 ft |
| 3/0 | 130 A | 155 A | 175 A | 125 A | 150 A | 190 ft |
| 4/0 | 150 A | 180 A | 205 A | 150 A | 175 A | 205 ft |
How to read it
Ampacity is what the wire can carry at each insulation temperature rating, with no more than 3 current-carrying wires together and 86 °F around them. NM-B cable (Romex) and UF-B have to use the 60 °C column, and NM-B is only made in copper, 14 to 2 AWG. THHN in conduit uses 75 °C, the most a breaker's terminals are rated for. The breaker columns are the biggest standard breaker at or under each ampacity. 14, 12 and 10 AWG copper are capped at 15, 20 and 30 A whatever the column says.
Run at 240 V is the longest one-way distance before a load at the full 75 °C breaker drops more than 3%. Half the load runs twice as far; 120 V runs half as far. For your own load and distance, use the wire size calculator. Don't know the amps? Watts to amps.
A load that runs 3 hours or more, like an EV charger or a heater, counts at 125%. A 48 A charger needs a 60 A breaker.
Where the numbers come from
- NFPA 70 (NEC), free access edition
- Encore Wire: ampacity table (NEC 310.16) and 240.4(D) limits
- Southwire: Romex SIMpull NM-B spec, 60 °C ampacity (2023 NEC)
- Southwire: SIMpull THHN/THWN-2 spec, 75 and 90 °C ampacity (2023 NEC)
- Okonite Engineering Handbook: conductor resistance and temperature correction
- Cerrowire: 3% voltage drop table