10 Amp Wire Size at 120 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 10 A load over a 120 ft (36.6 m) one-way run.
Copper Wire (≤3% Drop)12 AWG3.31 mm² · Drop: 1.97%
Aluminum Wire (≤3% Drop)10 AWGDrop: 4.91V (2.05%)
Voltage at Load End235.3 VLoss: 4.73 V (47.3 W)
Power & Breaker (125%)2.4 kW13A Breaker Recommended
All AWG & kcmil Wire Gauges for 10 Amps at 120 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 | 7.53 V (3.14%) | 232.5 V | 12.41 V (5.17%) | 75.3 W | ~ ≤5% |
| 12 AWG | 3.31 mm² | 20 A | 4.73 V (1.97%) | 235.3 V | 7.8 V (3.25%) | 47.3 W | ✓ PASS (≤3%) |
| 10 AWG | 5.26 mm² | 30 A | 2.98 V (1.24%) | 237.0 V | 4.91 V (2.05%) | 29.8 W | ✓ PASS (≤3%) |
| 8 AWG | 8.37 mm² | 50 A | 1.87 V (0.78%) | 238.1 V | 3.09 V (1.29%) | 18.7 W | ✓ PASS (≤3%) |
| 6 AWG | 13.3 mm² | 65 A | 1.18 V (0.49%) | 238.8 V | 1.94 V (0.81%) | 11.8 W | ✓ PASS (≤3%) |
| 4 AWG | 21.15 mm² | 85 A | 0.74 V (0.31%) | 239.3 V | 1.22 V (0.51%) | 7.4 W | ✓ PASS (≤3%) |
| 3 AWG | 26.67 mm² | 100 A | 0.59 V (0.24%) | 239.4 V | 0.97 V (0.4%) | 5.9 W | ✓ PASS (≤3%) |
| 2 AWG | 33.62 mm² | 115 A | 0.47 V (0.19%) | 239.5 V | 0.77 V (0.32%) | 4.7 W | ✓ PASS (≤3%) |
| 1 AWG | 42.41 mm² | 130 A | 0.37 V (0.15%) | 239.6 V | 0.61 V (0.25%) | 3.7 W | ✓ PASS (≤3%) |
| 1/0 AWG | 53.49 mm² | 150 A | 0.29 V (0.12%) | 239.7 V | 0.48 V (0.2%) | 2.9 W | ✓ PASS (≤3%) |
| 2/0 AWG | 67.43 mm² | 175 A | 0.23 V (0.1%) | 239.8 V | 0.38 V (0.16%) | 2.3 W | ✓ PASS (≤3%) |
| 3/0 AWG | 85.01 mm² | 200 A | 0.18 V (0.08%) | 239.8 V | 0.3 V (0.13%) | 1.8 W | ✓ PASS (≤3%) |
| 4/0 AWG | 107.2 mm² | 230 A | 0.15 V (0.06%) | 239.9 V | 0.24 V (0.1%) | 1.5 W | ✓ PASS (≤3%) |
| 250 kcmil | 126.7 mm² | 255 A | 0.12 V (0.05%) | 239.9 V | 0.2 V (0.08%) | 1.2 W | ✓ PASS (≤3%) |
| 300 kcmil | 152.0 mm² | 285 A | 0.1 V (0.04%) | 239.9 V | 0.17 V (0.07%) | 1.0 W | ✓ PASS (≤3%) |
| 350 kcmil | 177.3 mm² | 310 A | 0.09 V (0.04%) | 239.9 V | 0.15 V (0.06%) | 0.9 W | ✓ PASS (≤3%) |
| 400 kcmil | 202.7 mm² | 335 A | 0.08 V (0.03%) | 239.9 V | 0.13 V (0.05%) | 0.8 W | ✓ PASS (≤3%) |
| 500 kcmil | 253.4 mm² | 380 A | 0.06 V (0.03%) | 239.9 V | 0.1 V (0.04%) | 0.6 W | ✓ PASS (≤3%) |
| 600 kcmil | 304.0 mm² | 420 A | 0.05 V (0.02%) | 239.9 V | 0.08 V (0.04%) | 0.5 W | ✓ PASS (≤3%) |
| 750 kcmil | 380.0 mm² | 475 A | 0.04 V (0.02%) | 240.0 V | 0.07 V (0.03%) | 0.4 W | ✓ PASS (≤3%) |
| 1000 kcmil | 506.7 mm² | 545 A | 0.03 V (0.01%) | 240.0 V | 0.05 V (0.02%) | 0.3 W | ✓ PASS (≤3%) |
Frequently Asked Engineering Questions
What size copper wire do I need for 10 amps at 120 feet (240V)?
To stay within the NEC recommended 3% maximum voltage drop for a 10A load over 120 feet one-way at 240V (1-Phase), you need 12 AWG copper wire. This produces a voltage drop of 4.73V (1.97%) and delivers 235.3V at the load.
What size aluminum wire is required for 10 amps at 120 feet?
Using aluminum conductors (75°C rating), you should use 10 AWG to maintain voltage drop at 4.91V (2.05%).
What breaker size is needed for a 10A continuous load?
Under NEC 210.20(A), continuous loads require a circuit breaker rated at 125% of the continuous current (10A × 1.25 = 12.5A), which corresponds to a standard 13A circuit breaker.
Compare Other Distances & Amperages
10 Amp Wire Size by Distance (240V)
10A at 20 ft (240V)10A at 30 ft (240V)10A at 40 ft (240V)10A at 50 ft (240V)10A at 60 ft (240V)10A at 75 ft (240V)10A at 80 ft (240V)10A at 100 ft (240V)10A at 125 ft (240V)10A at 150 ft (240V)10A at 175 ft (240V)