Standard breaker sizes
Short answer: NEC 240.6(A) lists the standard breaker ratings: 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200 A and up. In a home panel you mostly see 15 and 20 A single-pole breakers for lights and outlets, 30–60 A double-pole breakers for 240 V appliances, and a 100, 150 or 200 A main.
All standard breaker sizes
NEC 240.6(A) sets the standard ampere ratings for fuses and inverse-time circuit breakers: 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500, 600 A, continuing up to 6,000 A. Manufacturers also make 1–10 A ratings for special equipment. "Standard" matters because NEC 240.4(B) lets you round up to the next standard size when a wire's ampacity doesn't match one.
Breaker sizes, watts and wire
| Breaker | Watts at 120 V | Watts at 240 V | Copper NM-B | Copper THHN, 75 °C |
|---|---|---|---|---|
| 15 A | 1,800 | 3,600 | 14 AWG | 14 AWG |
| 20 A | 2,400 | 4,800 | 12 AWG | 12 AWG |
| 25 A | 3,000 | 6,000 | 10 AWG | 10 AWG |
| 30 A | 3,600 | 7,200 | 10 AWG | 10 AWG |
| 40 A | 4,800 | 9,600 | 8 AWG | 8 AWG |
| 50 A | 6,000 | 12,000 | 6 AWG | 8 AWG |
| 60 A | 7,200 | 14,400 | 4 AWG | 6 AWG |
| 70 A | 8,400 | 16,800 | 4 AWG | 4 AWG |
| 80 A | 9,600 | 19,200 | 3 AWG | 4 AWG |
| 90 A | 10,800 | 21,600 | 2 AWG | 3 AWG |
| 100 A | 12,000 | 24,000 | 1 AWG | 3 AWG |
| 125 A | 15,000 | 30,000 | 1/0 AWG | 1 AWG |
| 150 A | 18,000 | 36,000 | 3/0 AWG | 1/0 AWG |
| 200 A | 24,000 | 48,000 | 250 kcmil | 3/0 AWG |
Which breaker for which circuit
| Breaker | Typical circuits |
|---|---|
| 15 A, single pole | Lighting and general bedroom/living-room outlets on 14 AWG copper. |
| 20 A, single pole | Kitchen countertop, bathroom, laundry and garage outlets (NEC 210.11 requires 20 A circuits for several of these), microwaves, dishwashers, disposals. |
| 20 A, double pole | 240 V baseboard heaters up to about 3,800 W, small window or mini-split AC units. |
| 30 A, double pole | Electric dryers, 4,500–5,500 W water heaters, 30 A generator inlets (L14-30), RV TT-30 outlets (single pole, 120 V). |
| 40 A, double pole | Electric ranges and cooktops, 32 A EV chargers. |
| 50 A, double pole | Larger ranges, 40 A EV chargers on a 14-50 outlet, 50 A generator inlets, RV 14-50 pedestals, hot tubs. |
| 60 A, double pole | 48 A EV chargers, subpanels, whole-house tankless heaters. |
| 100–200 A | Main breakers and subpanel feeders. |
Single pole, double pole, GFCI and AFCI
- Single-pole breakers take one slot and feed 120 V circuits.
- Double-pole breakers take two slots and feed 240 V circuits (or 120/240 V circuits with a neutral, like a range or dryer).
- GFCI breakers protect people from shock; the 2023 NEC requires GFCI protection in kitchens, bathrooms, garages, outdoors, laundry areas and for many 240 V appliance outlets (210.8).
- AFCI breakers detect arcing faults and are required for most 120 V living-area circuits in new work (210.12).
- Breakers must be the type listed for your panel. A breaker that "fits" a different brand's panel is not allowed unless it is classified for it.
How to pick the right size
Start from the load: amps × 1.25 if it runs three hours or more, then round up to the next standard size, then pick a wire that the breaker protects. The breaker size calculator does all three steps, and the appliance nameplate's "maximum overcurrent protection" always wins.
Safety. Never replace a breaker with a larger one to stop it tripping. The breaker protects the wire; a larger breaker on the same wire lets the wire overheat. Working inside a panel is dangerous even with the main off: the service conductors stay live.