Breaker size chart, every standard breaker rating and its wire size

Standard breaker sizes from NEC 240.6(A)

NEC 240.6(A) lists the standard ampere ratings for fuses and inverse time circuit breakers. The list below runs from 10 to 6000 amps. The 10 amp rating was added to the list in the 2023 edition, so on the 2020 code and older the list starts at 15. Fuses also come in 1, 3, 6 and 601 amp ratings. Nonstandard ratings are permitted, but nearly everything installed is on this list.

If a calculation lands between two standard sizes, you round up to the next one only when the rules in 240.4(B) allow it, and never above 800 amps. Above 800 amps the next lower standard size is used.

Breaker size to wire size chart, 15 to 400 amps

Each row gives the smallest conductor whose ampacity in NEC Table 310.16 is at least the breaker rating, in the 60°C column and the 75°C column. Use the 60°C column for NM cable (Romex) and for terminals marked 60°C, which covers most small breakers and devices. Use the 75°C column only when every part of the circuit, wire and both terminals, is rated 75°C. Copper at 15, 20 and 30 amps is held to 14, 12 and 10 AWG by the small conductor rule in 240.4(D) whatever the table says.

Aluminum and copper clad aluminum are shown without the 240.4(D) limits, so check that rule before using aluminum on a 15 or 20 amp circuit. Sizes here assume not more than three current carrying conductors in a raceway or cable at a 30°C ambient. Heat, bundling and long runs change the answer, see the voltage drop note below.

Continuous loads and the 125 percent rule

A continuous load runs for three hours or more. The breaker for a continuous load must be rated at least 125 percent of that load, which is the same as saying the breaker can carry only 80 percent of its rating continuously. A 48 amp EV charger therefore needs a 60 amp breaker, and a 32 amp charger needs a 40 amp breaker. Loads that are not continuous, such as most general purpose receptacles, are sized at 100 percent.

The table shows the most continuous load each common breaker can carry.

Breaker sizes for common appliance circuits

Appliance circuits follow the nameplate first. The appliance label gives the minimum circuit ampacity and the maximum breaker size, and the installation manual overrides any general chart, this one included. The pairings below are the common ones used in homes.

A 240 volt electric dryer is normally on a 30 amp double pole breaker with 10 AWG copper. A tank water heater with a 4500 watt element draws about 18.75 amps at 240 volts, which is 23.4 amps at 125 percent, so it normally gets a 30 amp breaker with 10 AWG copper. An electric range is most often on a 50 amp breaker with 6 AWG copper, though some ranges are rated for 40 amps with 8 AWG, so read the range nameplate before pulling wire. Air conditioners, heat pumps and mini splits use the minimum circuit ampacity and maximum overcurrent protection marked on the unit, and the breaker must not exceed that maximum.

Why sources disagree about 50 and 100 amp wire

The answers differ because of the column used. NM cable is limited to its 60°C ampacity, so a 50 amp breaker on NM cable needs 6 AWG copper. The same breaker on THHN wire in conduit, with 75°C terminals, can use 8 AWG copper. A 100 amp breaker needs 3 AWG copper at 75°C and 1 AWG at 60°C. Dwelling services have their own rule in NEC 310.12, covered on the wire size by amps chart.

Long runs and voltage drop

The wire sizes above are the code minimum for heat, not for voltage drop. On a long run the wire is often one or two sizes larger so the voltage at the load stays acceptable. A larger wire does not change the breaker size.

Breakers on transformer primaries and secondaries

A transformer is protected under NEC 450.3, not by the general rules above. The primary breaker is based on the primary full load amps and the secondary conductors have their own tap rules. To find the full load amps first, enter the kVA and voltage in the kVA to amps calculator, then compare against the breaker ratings in the first table. Pad mounted transformers with primaries over 1000 volts follow the separate over 1000 volt rules in the same section.

What are the standard breaker sizes

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 under NEC 240.6(A). The 2023 NEC adds 10 amps.

What size wire for a 50 amp breaker

6 AWG copper in the 60°C column, which covers NM cable and most terminals. 8 AWG copper is allowed where the wire and both terminals are rated 75°C. Aluminum needs 4 AWG at 60°C and 6 AWG at 75°C.

What size breaker for 8 gauge wire

Up to 40 amps on 60°C terminals and up to 50 amps where everything is rated 75°C, with a 40 amp breaker the usual choice.

What size breaker for a dryer

30 amps on a double pole breaker with 10 AWG copper, for a standard 240 volt electric dryer. Check the dryer nameplate.

What size breaker for a water heater

30 amps with 10 AWG copper for a 4500 watt tank heater. The 125 percent rule turns the 18.75 amp load into 23.4 amps, and 30 amps with 10 AWG copper is the usual pairing.

What size breaker for an EV charger

125 percent of the charger's continuous amps. A 32 amp charger needs a 40 amp breaker and a 48 amp charger needs a 60 amp breaker.

Can I use a 20 amp breaker on 14 gauge wire

No. Under 240.4(D) 14 AWG copper is limited to a 15 amp breaker, and a 20 amp breaker needs 12 AWG copper.