NEC 240.6(A)
Standard Breaker Sizes (NEC 240.6(A))
The complete list of standard breaker and fuse ampere ratings recognized by NEC 240.6(A), plus the next-standard-size rounding rule.
NEC 240.6(A) Standard Ampere Ratings
| Typical use | Standard ratings (A) | Notes |
|---|---|---|
| Branch circuits | 15, 20, 25, 30 | Common receptacle and lighting circuits |
| Small feeders / appliances | 35, 40, 45, 50, 60 | Ranges, dryers, EV, small subpanels |
| Feeders | 70, 80, 90, 100 | Subpanels, larger equipment |
| Services / large feeders | 110, 125, 150, 175, 200 | Dwelling and light commercial services |
| Large services | 225, 250, 300, 350, 400, 450, 500, 600 | Commercial and industrial |
| Distribution | 700, 800, 1000, 1200, 1600, 2000, 2500, 3000, 4000, 5000, 6000 | Switchboards and large gear |
Full standard set, in order: 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, 700, 800, 1000, 1200, 1600, 2000, 2500, 3000, 4000, 5000, 6000 A.
The Next-Standard-Size Rule
Conductor ampacities from NEC Table 310.16 rarely land exactly on a standard breaker size, so NEC 240.4(B) gives a rounding rule. When the conductor ampacity does not correspond to a standard rating, you may protect it with the next higher standard size, provided three conditions are met: the device is rated 800A or less, the conductors are not part of a multioutlet branch circuit supplying receptacles, and the next size up is genuinely the next standard value. Above 800A, NEC 240.4(C) reverses this: you must round down to a standard size at or below the conductor ampacity.
Worked Example
Conductor lands at 115A of ampacity
#2 copper at 75°C = 115A (NEC 310.16). 115A is not a standard size.
The standard sizes bracket it at 110A and 125A. Under NEC 240.4(B) (device under 800A, not a receptacle multioutlet circuit), you may round up to 125A. If the circuit supplied multiple receptacles, you would drop to the 110A device instead.
Frequently Asked Questions
What are the standard breaker sizes?
The standard breaker and fuse ampere ratings in NEC 240.6(A) are 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, 700, 800, 1000, 1200, 1600, 2000, 2500, 3000, 4000, 5000, and 6000 amps.
Is there a 55 amp breaker?
No, 55A is not a standard size in NEC 240.6(A). The standard ratings jump from 50A to 60A, so a 55A calculated load is normally protected at 60A. Nonstandard ratings do exist as listed devices but are not part of the standard 240.6(A) set.
What is the next standard breaker size above 70 amps?
The next standard size above 70A is 80A, then 90A, then 100A, per NEC 240.6(A). Below 70 the ratings step in 10A increments from 30A (30, 40, 45, 50, 60, 70).
Can I round up to the next standard breaker size?
Usually yes. NEC 240.4(B) lets you use the next higher standard rating when the conductor ampacity does not match a standard size, as long as the device is 800A or less and the circuit does not supply multiple receptacle outlets. Above 800A you must round down to the next standard size at or below the conductor ampacity, per 240.4(C).
What are the standard breaker sizes over 100 amps?
Above 100A the standard NEC 240.6(A) ratings are 110, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500, 600, 700, 800, 1000, 1200, 1600, 2000, 2500, 3000, 4000, 5000, and 6000 amps.
Related Calculators & Charts
Wire Ampacity Chart (310.16)
Match a conductor ampacity to the right standard breaker with the full copper and aluminum table.
Wire Size Calculator
Size the conductor for a load and get the breaker that protects it, rounding handled.
Ground Wire Size Chart (250.122)
The equipment grounding conductor is sized from that breaker rating, look it up here.
Have the sizes. Now match one to your load.
The right breaker depends on the conductor ampacity and the load type. The wire size calculator sizes the conductor and picks the standard breaker that protects it.