Wire Size for 40 Amp 100 Feet (120V)
| Standard | Wire Size | Ampacity | Volt Drop | Drop % |
|---|
| NEC (US) | AWG 4 (21.2 mm²) | 85 A | 2.41 V | 2.01% |
| IEC (EU) | 16 mm² | 76 A | 3.20 V | 2.66% |
| BS (UK) | 10 mm² | 57 A | 5.11 V | 4.26% |
| AS/NZS | 10 mm² | 57 A | 5.11 V | 4.26% |
About AWG 4
- Typical use
- 70–85 A feeders — sub-panel feeds, commercial equipment
- Max breaker
- 85 A
- Temperature rating
- 75 °C
- NEC reference
- NEC Table 310.16
Always verify local code requirements. Wire sizing depends on insulation type, ambient temperature, and conduit fill.
Adjacent Current Comparison
| Current | AWG | mm² | Ampacity | Drop % |
|---|
| 30 A | AWG 6 | 13.3 mm² | 65 A | 2.40% |
| 40 A | AWG 4 | 21.2 mm² | 85 A | 2.01% |
| 50 A | AWG 4 | 21.2 mm² | 85 A | 2.51% |
Adjacent Distance Comparison
| Distance | AWG | mm² | Ampacity | Drop % |
|---|
| 75 ft | AWG 6 | 13.3 mm² | 65 A | 2.40% |
| 100 ft | AWG 4 | 21.2 mm² | 85 A | 2.01% |
| 150 ft | AWG 3 | 26.7 mm² | 100 A | 2.39% |