15 amp wire size
A 15 amp circuit needs 14 AWG copper wire with 75 °C terminations. Aluminum wire is not used for circuits this small.
15 amp wire size by termination rating
| Termination rating | Copper | Aluminum |
|---|---|---|
| 60 °C, NM-B | 14 AWG | copper only |
| 75 °C, THHN | 14 AWG | copper only |
| Ground wire | 14 AWG | — |
15 amp wire size by distance at 120 V
Sizes that keep the voltage drop within 3% on a 120 V circuit loaded to the full 15 A, 75 °C terminations. The copper ground wire grows with the hot wires on long runs.
| One-way distance | Copper | Drop | Copper ground |
|---|---|---|---|
| 25 ft | 14 AWG | 2.0% | 14 AWG |
| 50 ft | 12 AWG | 2.5% | 12 AWG |
| 100 ft | 8 AWG | 2.0% | 8 AWG |
| 150 ft | 8 AWG | 2.9% | 8 AWG |
| 200 ft | 6 AWG | 2.5% | 6 AWG |
| 300 ft | 4 AWG | 2.3% | 4 AWG |
Check your own 15 amp run
What are you sizing for?
A
ft
From the panel to the load, not there and back
Voltage
Conductor
Termination rating
Result
12 AWG copper
The run is long: ampacity alone allows 14 AWG, but a larger wire keeps the drop within 3%.
- Breaker
- 15 A
- Voltage drop
- 3.0 V (2.5%)
- Volts at the load
- 117.0 V
- Ground wire
- 12 AWG copper
How it is calculated
- Breaker: 15 A rounded up to a standard size = 15 A.
- Smallest copper conductor rated for 15 A at 75 °C: 14 AWG.
- Drop = 2 × K × 15 A × 50 ft ÷ 6,530 cmil = 2.96 V, target 3% of 120 V.
What a 15 amp circuit is used for
- General lighting circuits
- Bedroom and living room outlets