Free Electrical Wire Size Calculator — NEC 310.15

Circuit Details

Circuit Load in amps

Circuit Voltage 120V / 240V / 208V

One-Way Wire Run panel to device

Wire Material

Wiring Method / Insulation

Conduit Fill (conductors in same raceway)

Ambient Temperature

Continuous load (on 3+ hours) — apply 125% per NEC 210.20

🔌

Enter your circuit details on the left and click Calculate to get the correct wire gauge per NEC 310.15.

NEC 310.15 Ampacity Reference — Copper Conductors (75°C, 3 conductors in raceway)

AWG / kcmil	60°C Ampacity	75°C Ampacity	90°C Ampacity	Typical Use
14 AWG	15A	20A	25A	General purpose 15A circuits
12 AWG	20A	25A	30A	Kitchen circuits, 20A branch
10 AWG	30A	35A	40A	Dryer, water heater, A/C
8 AWG	40A	50A	55A	Range, EV charger (40A)
6 AWG	55A	65A	75A	EV charger (50A), sub-panel feed
4 AWG	70A	85A	95A	Sub-panel, large A/C
3 AWG	85A	100A	110A	100A sub-panel feeder
2 AWG	95A	115A	130A	Service entrance, large feeder
1 AWG	110A	130A	150A	150A service
1/0 AWG	125A	150A	170A	150–200A feeder
2/0 AWG	145A	175A	195A	200A service entrance
3/0 AWG	165A	200A	225A	200A main service, large panel
4/0 AWG	195A	230A	260A	Large commercial service
250 kcmil	215A	255A	290A	Large commercial/industrial
350 kcmil	260A	310A	350A	400A service entrance
500 kcmil	320A	380A	430A	Large industrial service

Disclaimer: This calculator provides general reference information based on NEC 310.15 and standard derating methods. Always verify wire sizing with your local Authority Having Jurisdiction (AHJ) and the current adopted NEC edition in your jurisdiction. Environmental conditions, specific equipment ratings, and local amendments may affect the required conductor size. The licensed electrician is solely responsible for all code compliance decisions.