Quick reference · Wire size for a breaker
What gauge copper or aluminum wire pairs with a 15 to 100 amp breaker — the common 75°C sizes electricians reach for, with the NEC caveats that actually matter.
| Breaker | Copper | Aluminum | Typical use |
|---|---|---|---|
| 15 A | 14 AWG | 12 AWG | Lighting & general-purpose receptacles |
| 20 A | 12 AWG | 10 AWG | Kitchen, bath, laundry, small-appliance circuits |
| 30 A | 10 AWG | 8 AWG | Electric water heater, dryer, small A/C |
| 40 A | 8 AWG | 6 AWG | Electric range, larger A/C |
| 50 A | 6 AWG | 4 AWG | Range, EV charger, small sub-panel |
| 60 A | 4 AWG | 3 AWG | Sub-panel feeder, large A/C |
| 70 A | 4 AWG | 3 AWG | Sub-panel feeder |
| 80 A | 3 AWG | 2 AWG | Sub-panel feeder |
| 90 A | 2 AWG | 1 AWG | Feeder |
| 100 A | 1 AWG | 1/0 AWG | 100 A sub-panel or feeder |
Common copper/aluminum sizes at 75°C terminations. Exact size depends on termination temperature rating, continuous load (125% rule), ambient/conductor-count derating, and voltage drop — verify against NEC Table 310.16 and 240.4. Dwelling services/feeders may use smaller conductors under NEC 310.12 (e.g., 100 A = #4 Cu, 200 A = 2/0 Cu).
The breaker protects the wire, so the conductor must be able to carry at least the breaker's rating. This chart shows the common copper and aluminum sizes at 75°C terminations for the breakers you see most on residential and light-commercial work.
Three things move the answer off this chart: a continuous load (3+ hours) requires sizing conductor and breaker at 125% of the load; the termination temperature rating of the breaker/lug (often 60°C for small equipment) can require a larger conductor; and long runs may need an upsize for voltage drop. Always confirm against the full ampacity chart (310.16).
Check a long run with the voltage drop calculator, and size the raceway with the conduit fill calculator. Field PM keeps the panel schedules and inspection records together so the install matches the design.
A 50 A circuit is commonly wired with 6 AWG copper or 4 AWG aluminum at 75°C terminations. For a continuous 50 A load (on for 3+ hours) the conductor and breaker must be sized at 125%, which can push you to a larger conductor — always verify against NEC 310.16 and 240.4.
A 100 A feeder is commonly 1 AWG copper or 1/0 AWG aluminum at 75°C. Dwelling services and feeders may use smaller conductors under NEC 310.12 — for example, 4 AWG copper or 2 AWG aluminum for a 100 A dwelling service.
It reflects common 75°C copper/aluminum sizing, but the exact conductor depends on the termination temperature rating, continuous load (the 125% rule), ambient and conductor-count derating, and voltage drop. Use it as a quick reference and confirm with NEC Table 310.16 and 240.4(D).
Aluminum has lower conductivity than copper, so for the same ampacity it must be roughly one to two AWG sizes larger — for example, 6 AWG copper and 4 AWG aluminum both carry about 50–65 A at 75°C.
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