Standard breaker sizes
Standard breaker sizes are the ampere ratings that NEC 240.6(A) lists as standard for fuses and inverse-time circuit breakers. The list runs from 15 A to 6,000 A; manufacturers build breakers at these ratings, and other NEC rules, such as the next-size-up allowance of 240.4(B), refer back to it.
Standard ampere ratings, NEC 240.6(A)
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, 700, 800, 1,000, 1,200, 1,600, 2,000, 2,500, 3,000, 4,000, 5,000, 6,000 A.
Fuses only: 1, 3, 6, 10, 601 A.
2017 and 2020 wording; the 2023 edition also lists 10 A for circuit breakers. Verify against the NEC edition adopted locally.
Where the list comes from
In the 2017 and 2020 editions, 240.6(A) gives the list as a single sentence of ratings for fuses and inverse-time circuit breakers, followed by additional standard ratings that apply to fuses only: 1, 3, 6, 10 and 601 A. The 2023 edition sets the same ratings out as Table 240.6(A) and, according to published summaries of the changes, adds 10 A as a standard rating for circuit breakers as well, tied to the new 10 A circuits permitted with 14 AWG copper-clad aluminum. The edition adopted locally decides which list applies.
A standard rating says nothing about which breaker belongs on a given circuit. That comes from the load, the conductor and the equipment's own instructions; the list only fixes the steps between available sizes.
Common residential breaker sizes
| Breaker | Poles | Copper, NM-B (60 °C) | Copper, 75 °C | Typical loads |
|---|---|---|---|---|
| 15 A | 1 or 2 | 14 AWG | 14 AWG | General lighting and receptacle circuits, bedroom and living room outlets |
| 20 A | 1 or 2 | 12 AWG | 12 AWG | Kitchen countertop, bathroom, laundry and garage receptacles; dishwasher, disposal |
| 30 A | 2 | 10 AWG | 10 AWG | Electric dryer, tank water heater, small air conditioner, TT-30 RV outlet |
| 40 A | 2 | 8 AWG | 8 AWG | Electric range or cooktop, 32 A EV charger, heat pump |
| 50 A | 2 | 6 AWG | 8 AWG | Large range, 14-50 RV outlet, 40 A EV charger, small subpanel |
| 60 A | 2 | 4 AWG | 6 AWG | Subpanel feeder, hot tub, 48 A EV charger |
| 100 A | 2 | Beyond NM-B | 3 AWG | Small dwelling service or main breaker, subpanel feeder |
| 150 A | 2 | Beyond NM-B | 1/0 AWG | Dwelling service upgrade, large subpanel feeder |
| 200 A | 2 | Beyond NM-B | 3/0 AWG | Typical new dwelling service and main breaker |
Minimum sizes at the full breaker rating, with the 240.4(D) limits; dwelling services may use the 83% sizes of NEC 310.12. Manufacturer chart values (2017 NEC basis). Verify against the NEC edition adopted locally.
Adjustable-trip breakers
Large breakers often have an adjustable long-time pickup. Under 240.6(B), the rating of an adjustable-trip breaker is the maximum setting it can be adjusted to, unless the setting is protected as 240.6(C) describes: behind a sealable cover, a locked door or a removable and sealable cover, with access limited to qualified persons. In that case the rating is the actual setting.
What next size up means
Conductor ampacities seldom land exactly on a standard rating. NEC 240.4(B) allows the next higher standard rating above the conductor's ampacity when three conditions hold: the conductors are not part of a branch circuit supplying more than one receptacle for cord-and-plug-connected portable loads, the ampacity does not itself match a standard rating, and the next higher rating does not exceed 800 A.
A 6 AWG copper NM-B cable rated 55 A may therefore sit on a 60 A breaker, provided its calculated load does not exceed 55 A. A conductor whose ampacity is 40 A, a standard rating, gets no allowance: its breaker is 40 A.
Above 800 A the allowance ends. Under 240.4(C), when the overcurrent device is rated over 800 A, the ampacity of the conductors it protects must be equal to or greater than the device's rating, and the NEC lists the ratings in that range as 1,000, 1,200, 1,600 A and up.
The small-conductor limits
NEC 240.4(D) overrides both the ampacity tables and the next-size-up rule for the smallest conductors. 14 AWG copper may be protected at no more than 15 A, 12 AWG copper at 20 A and 10 AWG copper at 30 A; 12 AWG and 10 AWG aluminum at 15 A and 25 A. Motor, air-conditioning and other circuits listed in 240.4(G) follow their own articles instead.
Single-pole and double-pole breakers
A single-pole breaker connects to one hot bus in the panel and protects a 120 V circuit. A double-pole breaker spans both legs of a 120/240 V panel, supplies 240 V loads such as dryers, ranges, water heaters and air conditioners, and opens both conductors together when either side trips.
A multiwire branch circuit, two hot conductors sharing one neutral, needs a means that disconnects both hots at the same time (210.4(B)): a double-pole breaker or two single-pole breakers joined by an identified handle tie. Tandem or twin breakers, which put two circuits in one space, may be used only in panels whose labels list them for that space.
Continuous loads and the 80% figure
Most breakers in panelboards are not rated for 100% continuous loading. Where a load runs for 3 hours or more, the NEC sizes the breaker at 125% of the continuous load (210.20(A) for branch circuits, 215.3 for feeders), which is the same as loading a standard breaker to no more than 80% of its rating. A 40 A breaker supplies a 32 A EV charger for that reason.
Interrupting rating, AFCI and GFCI
The ampere rating is the current a breaker carries continuously; the interrupting rating is the fault current it can safely clear. NEC 110.9 requires the interrupting rating to be at least the available fault current. Residential breakers are commonly rated 10,000 A interrupting, with 22,000 A versions where the utility transformer is large or close; the available fault current calculator estimates the figure at a panel.
Many 15 A and 20 A dwelling circuits also need arc-fault (AFCI) protection under 210.12, and receptacles in kitchens, bathrooms, garages, outdoors and other locations need ground-fault (GFCI) protection under 210.8. Both are available as breakers in the standard ratings, as are dual-function AFCI/GFCI breakers.
Frequently asked questions
What are the standard breaker sizes?
NEC 240.6(A) lists 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, 1,000, 1,200, 1,600, 2,000, 2,500, 3,000, 4,000, 5,000 and 6,000 A. The 2023 edition also lists 10 A.
Is 55 amps a standard breaker size?
No. The ratings step from 50 A to 60 A. A conductor rated 55 A may be protected by a 60 A breaker under the next-size-up rule of 240.4(B) when the other conditions of that rule are met.
What breaker sizes are common in a house?
15 A and 20 A single-pole breakers for lighting and receptacles, 30 A to 60 A double-pole breakers for dryers, water heaters, ranges, EV chargers and subpanels, and a 100 A, 150 A or 200 A main breaker.
Can a larger breaker be installed on the same wire?
Only if the conductor's ampacity, the 240.4(D) small-conductor limits and the next-size-up rule all allow it. Raising the breaker to stop nuisance trips without changing the wire leaves the conductor unprotected.
What is the difference between a single-pole and double-pole breaker?
A single-pole breaker protects one 120 V hot conductor. A double-pole breaker protects two hot conductors on opposite legs, for 240 V or 120/240 V loads, and trips both at once.