4 gauge wire at a glance
| Diameter (bare copper) | 0.2043 in (5.19 mm) |
|---|---|
| Cross-section area | 21.15 mm² (41,740 circular mils) |
| Copper ampacity, 60°C / 75°C / 90°C | 70 / 85 / 95 A |
| Maximum breaker (copper) | 80 A |
| Aluminum ampacity, 60°C / 75°C / 90°C | 55 / 65 / 75 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 4 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 4 AWG copper within 3% drop, by current and voltage.
| Current | 12 V DC | 24 V DC | 120 V AC | 240 V AC |
|---|---|---|---|---|
| 40 A | 15 ft | 29 ft | 146 ft | 291 ft |
| 70 A | 8.3 ft | 17 ft | 83 ft | 166 ft |
| 85 A | 6.9 ft | 14 ft | 69 ft | 137 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 4 gauge wire is used for
- Sub panels of up to 70 A in cable, or 80 A in conduit
- A 100 A single-phase dwelling service in copper, under NEC 310.12
- Large 12 V battery and inverter cables, over short distances
- Big heat pumps and shop equipment
Cable type and the rules
4/3 NM-B (Romex) is rated 70 A. In conduit, 4 AWG THHN is rated 85 A at 75°C. The 100 A dwelling service use is a special case and only applies to a main service or feeder, not a sub panel.
Neighboring sizes
| Gauge | Diameter | Copper amps (75°C, with NEC 240.4(D) limits) |
|---|---|---|
| 6 AWG | 0.1620 in | 65 A |
| 4 AWG | 0.2043 in | 85 A |
| 3 AWG | 0.2294 in | 100 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 4 gauge wire handle?
70 amps at 60°C, 85 amps at 75°C and 95 amps at 90°C for copper.
What size breaker for 4 gauge wire?
A 70 amp breaker for NM-B cable, or 80 amps in conduit on 75°C terminals.
How far can 4 gauge wire run at 240 volts?
About 166 feet one way at 70 A within 3% drop.
Can 4 gauge wire be used for a 100 amp panel?
Only as a single-family dwelling service or main feeder under NEC 310.12. For a sub panel use 3 AWG copper.