8 gauge wire at a glance
| Diameter (bare copper) | 0.1285 in (3.26 mm) |
|---|---|
| Cross-section area | 8.37 mm² (16,510 circular mils) |
| Copper ampacity, 60°C / 75°C / 90°C | 40 / 50 / 55 A |
| Maximum breaker (copper) | 50 A |
| Aluminum ampacity, 60°C / 75°C / 90°C | 30 / 40 / 45 A |
14 AWG copper is limited to 15 A, 12 AWG to 20 A and 10 AWG to 30 A, and 12 and 10 AWG aluminum to 15 A and 25 A, by the overcurrent rules in NEC 240.4(D), even where the ampacity table lists more.
How far can 8 gauge wire run?
Current is only half the story. The wire loses voltage over distance, and the NEC recommends staying within 3%. This table gives the longest one-way run of 8 AWG copper within 3% drop, by current and voltage.
| Current | 12 V DC | 24 V DC | 120 V AC | 240 V AC |
|---|---|---|---|---|
| 20 A | 12 ft | 23 ft | 115 ft | 230 ft |
| 40 A | 5.8 ft | 12 ft | 58 ft | 115 ft |
| 50 A | 4.6 ft | 9.2 ft | 46 ft | 92 ft |
Use the voltage drop calculator for another size, current or limit. For 12 V runs by size, see the 12V wire gauge chart.
What 8 gauge wire is used for
- Electric ranges and ovens, using 8 AWG THHN in conduit on a 50 A breaker
- Level 2 EV chargers on a 40 A circuit
- Tankless water heaters and welders
- Heavy 12 V and 24 V DC runs for solar and RVs
Cable type and the rules
8/2 and 8/3 NM-B (Romex) is rated 40 A. In conduit, 8 AWG THHN is rated 50 A at 75°C. Both are common, so know which you have before you pick a breaker.
Neighboring sizes
| Gauge | Diameter | Copper amps (75°C, with NEC 240.4(D) limits) |
|---|---|---|
| 10 AWG | 0.1019 in | 30 A |
| 8 AWG | 0.1285 in | 50 A |
| 6 AWG | 0.1620 in | 65 A |
The wire gauge chart covers every size, and the amps per wire size table lists them in all three temperature columns.
Frequently asked questions
How many amps can 8 gauge wire handle?
40 amps at 60°C, 50 amps at 75°C and 55 amps at 90°C for copper.
What size breaker for 8 gauge wire?
A 40 amp breaker for NM-B cable, or 50 amps for THHN in conduit on 75°C terminals.
How far can 8 gauge wire run at 240 volts?
About 92 feet one way at 50 A within 3% drop, and about 115 feet at 40 A.
What is the diameter of 8 gauge wire?
0.1285 inches, or 3.26 mm, for the bare conductor.