What Size Wire Do I Need? (NEC Wire Size Chart)

The wire size you need depends mainly on the current (amps) the circuit carries and the conductor material. The chart below lists common minimum sizes from the 75°C column of NEC Table 310.16 — the column most terminations use.

Amps	Copper (75°C)	Aluminum (75°C)
15 A	14 AWG	—
20 A	12 AWG	—
30 A	10 AWG	10 AWG
40 A	8 AWG	8 AWG
50 A	8 AWG	6 AWG
60 A	6 AWG	4 AWG
100 A	3 AWG	1 AWG
200 A	3/0 AWG	250 kcmil

Three things that change the answer

Derating: high ambient temperature or more than three current-carrying conductors in a raceway lowers capacity — you may need to go up a size.
Terminations (110.14(C)): most breakers and lugs are rated 60°C or 75°C, so you generally can't use the higher 90°C ampacity even with 90°C-rated wire.
Voltage drop: on long runs, upsize to keep drop within about 3%.

Dwelling services and feeders

For an individual dwelling's main service or feeder, NEC 310.12 permits somewhat smaller conductors (for example, a 200 A service commonly uses 2/0 copper or 4/0 aluminum). Use that section for those specific cases.

Always confirm the final size with the ampacity calculator after entering your actual ambient temperature and conductor count.

Open the free Wire Ampacity Calculator →

Frequently asked questions

What size wire do I need for 50 amps?

Per NEC Table 310.16 (75°C column), 50 amps needs 8 AWG copper or 6 AWG aluminum, before derating. Confirm terminations are 75°C-rated and apply derating for heat or bundling.

What size wire for a 100 amp subpanel?

From the 75°C column, 100 amps needs 3 AWG copper or 1 AWG aluminum. Many installers go larger for margin and voltage drop. A dwelling feeder may use smaller per NEC 310.12.

Does wire size depend on copper vs aluminum?

Yes. Aluminum carries less current per size, so it generally needs to be one to two sizes larger than copper for the same amperage.

All Codewire calculators · Verify against the NEC edition adopted by your AHJ.