50 Amp Wire Size at 40 Feet (240V Split-Phase (US Dryer / EV / Subpanel))
Complete conductor sizing, Ohm's law voltage drop, $I^2R$ line power loss, and circuit breaker specification for a 50 A load over a 40 ft (12.2 m) one-way run.
Copper Wire (≤3% Drop)8 AWG8.37 mm² · Drop: 1.3%
Aluminum Wire (≤3% Drop)6 AWGDrop: 3.24V (1.35%)
Voltage at Load End236.9 VLoss: 3.12 V (155.9 W)
Power & Breaker (125%)12.0 kW63A Breaker Recommended
All AWG & kcmil Wire Gauges for 50 Amps at 40 Feet (240V)
| Wire Gauge | Metric Area | NEC 75°C Cu Ampacity | Copper Voltage Drop | Load Voltage | Aluminum Drop | Line Loss ($I^2R$) | NEC Status |
|---|---|---|---|---|---|---|---|
| 14 AWG | 2.08 mm² | 15 A | 12.54 V (5.23%) | 227.5 V | 20.69 V (8.62%) | 627.2 W | Drop/Amp High |
| 12 AWG | 3.31 mm² | 20 A | 7.88 V (3.28%) | 232.1 V | 13.0 V (5.42%) | 394.1 W | Drop/Amp High |
| 10 AWG | 5.26 mm² | 30 A | 4.96 V (2.07%) | 235.0 V | 8.18 V (3.41%) | 248.0 W | Drop/Amp High |
| 8 AWG | 8.37 mm² | 50 A | 3.12 V (1.3%) | 236.9 V | 5.14 V (2.14%) | 155.9 W | ✓ PASS (≤3%) |
| 6 AWG | 13.3 mm² | 65 A | 1.96 V (0.82%) | 238.0 V | 3.24 V (1.35%) | 98.1 W | ✓ PASS (≤3%) |
| 4 AWG | 21.15 mm² | 85 A | 1.23 V (0.51%) | 238.8 V | 2.03 V (0.85%) | 61.7 W | ✓ PASS (≤3%) |
| 3 AWG | 26.67 mm² | 100 A | 0.98 V (0.41%) | 239.0 V | 1.61 V (0.67%) | 48.9 W | ✓ PASS (≤3%) |
| 2 AWG | 33.62 mm² | 115 A | 0.78 V (0.32%) | 239.2 V | 1.28 V (0.53%) | 38.8 W | ✓ PASS (≤3%) |
| 1 AWG | 42.41 mm² | 130 A | 0.62 V (0.26%) | 239.4 V | 1.01 V (0.42%) | 30.8 W | ✓ PASS (≤3%) |
| 1/0 AWG | 53.49 mm² | 150 A | 0.49 V (0.2%) | 239.5 V | 0.8 V (0.34%) | 24.4 W | ✓ PASS (≤3%) |
| 2/0 AWG | 67.43 mm² | 175 A | 0.39 V (0.16%) | 239.6 V | 0.64 V (0.27%) | 19.3 W | ✓ PASS (≤3%) |
| 3/0 AWG | 85.01 mm² | 200 A | 0.31 V (0.13%) | 239.7 V | 0.51 V (0.21%) | 15.3 W | ✓ PASS (≤3%) |
| 4/0 AWG | 107.2 mm² | 230 A | 0.24 V (0.1%) | 239.8 V | 0.4 V (0.17%) | 12.2 W | ✓ PASS (≤3%) |
| 250 kcmil | 126.7 mm² | 255 A | 0.21 V (0.09%) | 239.8 V | 0.34 V (0.14%) | 10.3 W | ✓ PASS (≤3%) |
| 300 kcmil | 152.0 mm² | 285 A | 0.17 V (0.07%) | 239.8 V | 0.28 V (0.12%) | 8.6 W | ✓ PASS (≤3%) |
| 350 kcmil | 177.3 mm² | 310 A | 0.15 V (0.06%) | 239.9 V | 0.24 V (0.1%) | 7.4 W | ✓ PASS (≤3%) |
| 400 kcmil | 202.7 mm² | 335 A | 0.13 V (0.05%) | 239.9 V | 0.21 V (0.09%) | 6.4 W | ✓ PASS (≤3%) |
| 500 kcmil | 253.4 mm² | 380 A | 0.1 V (0.04%) | 239.9 V | 0.17 V (0.07%) | 5.1 W | ✓ PASS (≤3%) |
| 600 kcmil | 304.0 mm² | 420 A | 0.09 V (0.04%) | 239.9 V | 0.14 V (0.06%) | 4.3 W | ✓ PASS (≤3%) |
| 750 kcmil | 380.0 mm² | 475 A | 0.07 V (0.03%) | 239.9 V | 0.11 V (0.05%) | 3.4 W | ✓ PASS (≤3%) |
| 1000 kcmil | 506.7 mm² | 545 A | 0.05 V (0.02%) | 239.9 V | 0.08 V (0.04%) | 2.6 W | ✓ PASS (≤3%) |
Frequently Asked Engineering Questions
What size copper wire do I need for 50 amps at 40 feet (240V)?
To stay within the NEC recommended 3% maximum voltage drop for a 50A load over 40 feet one-way at 240V (1-Phase), you need 8 AWG copper wire. This produces a voltage drop of 3.12V (1.3%) and delivers 236.9V at the load.
What size aluminum wire is required for 50 amps at 40 feet?
Using aluminum conductors (75°C rating), you should use 6 AWG to maintain voltage drop at 3.24V (1.35%).
What breaker size is needed for a 50A continuous load?
Under NEC 210.20(A), continuous loads require a circuit breaker rated at 125% of the continuous current (50A × 1.25 = 62.5A), which corresponds to a standard 63A circuit breaker.
Compare Other Distances & Amperages
50 Amp Wire Size by Distance (240V)
50A at 20 ft (240V)50A at 30 ft (240V)50A at 50 ft (240V)50A at 60 ft (240V)50A at 75 ft (240V)50A at 80 ft (240V)50A at 100 ft (240V)50A at 120 ft (240V)50A at 125 ft (240V)50A at 150 ft (240V)50A at 175 ft (240V)