Wire Size Calculator
Enter the load — get the AWG. Add a distance to auto-check voltage drop and upsize if needed.
How the size is chosen
The calculator walks the NEC 310.16 ampacity column for your material and termination rating and returns the smallest conductor whose ampacity meets the load. For 14, 12 and 10 AWG it automatically applies the NEC 240.4(D) small-conductor caps (15/20/30 A on copper) — the rule that trips up most quick chart lookups. If you enter a distance, it also checks the run against the 3% voltage-drop guideline and recommends the next size up when the run is too long.
Typical picks (copper, 75°C)
| Load | Copper | Common use |
|---|---|---|
| 15 A | 14 AWG | lighting circuits |
| 20 A | 12 AWG | receptacles, small appliance |
| 30 A | 10 AWG | dryer, water heater |
| 40 A | 8 AWG | range |
| 50 A | 8 AWG | EV charger (non-continuous rating) |
| 60 A | 6 AWG | subpanel feeder |
| 100 A | 3 AWG | subpanel / small service |
Continuous loads (EV charging, heating) must be sized at 125% of the load per NEC 210.19 — enter the adjusted amps. Derating for ambient heat or bundled conductors is not included in v1.
Related: full ampacity chart · voltage drop calculator · conduit fill calculator