What wire size does each breaker need, what ground wire goes with it, and how much load it can actually carry. Conductor sizes follow the 75°C column of NEC Table 310.16; grounds follow NEC Table 250.122.
| Breaker | Copper | Aluminum | Ground (Cu) | Max continuous | Poles | Typical use |
|---|---|---|---|---|---|---|
| 15A | 14 AWG | 12 AWG | 14 AWG | 12 A | Single-pole | General lighting circuits |
| 20A | 12 AWG | 10 AWG | 12 AWG | 16 A | Single-pole | Kitchen small-appliance circuits |
| 30A | 10 AWG | 8 AWG | 10 AWG | 24 A | Double-pole | Electric clothes dryers |
| 40A | 8 AWG | 6 AWG | 10 AWG | 32 A | Double-pole | Electric ranges and cooktops |
| 50A | 6 AWG | 4 AWG | 10 AWG | 40 A | Double-pole | Electric ranges |
| 60A | 6 AWG | 4 AWG | 10 AWG | 48 A | Double-pole | Sub-panels |
| 100A | 1 AWG | 1/0 AWG | 8 AWG | 80 A | Double-pole | Main service for a small home |
| 200A | 3/0 AWG* | 250 kcmil* | 6 AWG | 160 A | Double-pole | Standard main service for a modern single-family home |
Maximum continuous load is 80% of the breaker rating, the inverse of the 125% sizing requirement in NEC 210.20(A). Non-continuous loads may use the full breaker rating. Sizes up to 100 A meet the 60°C column (NM-B and any termination) except 60 A, which assumes 75°C terminations. * 200 A per NEC Table 310.16 at 75°C; a one-family dwelling service or main feeder may use 2/0 copper or 4/0 aluminum under NEC 310.12.
This is the single idea behind every number on this page. A circuit breaker exists to open the circuit before the conductor overheats. It is chosen to match the wire, not the appliance. An appliance that trips a correctly sized breaker is drawing more than the circuit was built for — the answer is a bigger circuit, never a bigger breaker on the same wire.
Three code rules set the ceiling, and the smallest one wins. Table 310.16 gives the conductor ampacity. NEC 240.4(D) caps 14, 12 and 10 AWG copper at 15, 20 and 30 A regardless of what the table says. NEC 110.14(C) limits you to the termination temperature rating, normally 75°C, even when the conductor is 90°C THHN.
Then two more can pull the required conductor larger: 310.15 derating for hot ambients or crowded raceways, and voltage drop on long runs.
15 A takes 14 AWG copper, 20 A takes 12 AWG, 30 A takes 10 AWG, 40 A takes 8 AWG, 50 A takes 6 AWG, 60 A takes 6 AWG with 75°C terminations (4 AWG with NM-B), 100 A takes 1 AWG (3 AWG with 75°C terminations), and 200 A takes 3/0 (2/0 on a dwelling service under NEC 310.12). Aluminum needs roughly two gauge sizes larger for the same rating.
No. The breaker protects the wire, not the appliance. Installing a larger breaker on existing conductors removes that protection and is one of the most common causes of electrical fires. If a breaker trips repeatedly, the fix is a load calculation and possibly a new circuit — never a larger breaker on the same wire.
That applies to continuous loads — those running three hours or more. NEC 210.20(A) requires the overcurrent device to be rated at 125% of a continuous load, which is the same as limiting the continuous load to 80% of the breaker. Non-continuous loads may use the full rating.
From NEC Table 250.122: 14 AWG copper for 15 A, 12 AWG for 20 A, 10 AWG for anything up to 60 A, 8 AWG up to 100 A, and 6 AWG up to 200 A. The table gives maximum device ratings, so you round up to the next listed row.