Wire Size for 340 Amps
Typical copper and aluminum wire gauges for 340 amps across common run lengths on a 120V circuit, sized to keep voltage drop under 3% and respect the NEC 240.4(D) small-conductor rule. Actual install sizing depends on conductor material, insulation/termination temperature rating, cable type, ambient and bundling derates, and local code.
340A Wire Gauge by Distance
| Distance | Copper Gauge | Aluminum Gauge | V-Drop (Cu) | NEC Status |
|---|---|---|---|---|
| 25 ft | 500 kcmil | 750 kcmil | 0.4386V (0.3655%) | OK |
| 50 ft | 500 kcmil | 750 kcmil | 0.8772V (0.731%) | OK |
| 75 ft | 500 kcmil | 750 kcmil | 1.32V (1.1%) | OK |
| 100 ft | 500 kcmil | 750 kcmil | 1.75V (1.46%) | OK |
| 125 ft | 500 kcmil | 750 kcmil | 2.19V (1.83%) | OK |
| 150 ft | 500 kcmil | 750 kcmil | 2.63V (2.19%) | OK |
| 175 ft | 500 kcmil | 750 kcmil | 3.07V (2.56%) | OK |
| 200 ft | 500 kcmil | no aluminum pick | 3.51V (2.92%) | OK |
| 250 ft | 750 kcmil | no aluminum pick | 2.91V (2.42%) | OK |
| 300 ft | 750 kcmil | no aluminum pick | 3.49V (2.91%) | OK |
| 400 ft | Exceeds available gauges | |||
| 500 ft | Exceeds available gauges | |||
Aluminum is not typical for 10 AWG and smaller branch-circuit conductors in residential settings. Copper gauges use the NEC 240.4(D) branch-circuit cap, not raw 75°C ampacity.
Also Calculate
Other Amperages
This calculator provides estimates for reference purposes only. Always consult a licensed electrician and verify compliance with the National Electrical Code (NEC) and local electrical codes before performing any electrical work.