Wire Size for 20 Amp 300 Feet (120V)
| Standard | Wire Size | Ampacity | Volt Drop | Drop % |
|---|
| NEC (US) | AWG 3 (26.7 mm²) | 100 A | 2.87 V | 2.39% |
| IEC (EU) | 25 mm² | 101 A | 3.07 V | 2.56% |
| BS (UK) | 16 mm² | 76 A | 4.79 V | 3.99% |
| AS/NZS | 16 mm² | 76 A | 4.79 V | 3.99% |
About AWG 3
- Typical use
- 85–100 A feeders — large sub-panels, commercial branch circuits
- Max breaker
- 100 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 % |
|---|
| 15 A | AWG 4 | 21.2 mm² | 85 A | 2.26% |
| 20 A | AWG 3 | 26.7 mm² | 100 A | 2.39% |
| 30 A | AWG 2 | 33.6 mm² | 115 A | 2.85% |
Adjacent Distance Comparison
| Distance | AWG | mm² | Ampacity | Drop % |
|---|
| 200 ft | AWG 4 | 21.2 mm² | 85 A | 2.01% |
| 300 ft | AWG 3 | 26.7 mm² | 100 A | 2.39% |