Wire Size for 387 Amps
Typical copper and aluminum wire gauges for 387 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.
387A Wire Gauge by Distance
| Distance | Copper Gauge | Aluminum Gauge | V-Drop (Cu) | NEC Status |
|---|---|---|---|---|
| 25 ft | 750 kcmil | no aluminum pick | 0.3309V (0.2757%) | OK |
| 50 ft | 750 kcmil | no aluminum pick | 0.6618V (0.5515%) | OK |
| 75 ft | 750 kcmil | no aluminum pick | 0.9927V (0.8272%) | OK |
| 100 ft | 750 kcmil | no aluminum pick | 1.32V (1.1%) | OK |
| 125 ft | 750 kcmil | no aluminum pick | 1.65V (1.38%) | OK |
| 150 ft | 750 kcmil | no aluminum pick | 1.99V (1.65%) | OK |
| 175 ft | 750 kcmil | no aluminum pick | 2.32V (1.93%) | OK |
| 200 ft | 750 kcmil | no aluminum pick | 2.65V (2.21%) | OK |
| 250 ft | 750 kcmil | no aluminum pick | 3.31V (2.76%) | OK |
| 300 ft | Exceeds available gauges | |||
| 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.