Breaker size chart

Name: Breaker size chart
Creator: Calculate.diy

14 AWG copper wire takes a breaker of up to 15 A, 12 AWG up to 20 A, 10 AWG up to 30 A and 8 AWG up to 50 A with 75 °C terminations (40 A in NM-B cable).

Largest standard breaker for each copper and aluminum wire size at 60 °C and 75 °C terminations; NM-B cable uses the copper 60 °C column and is made up to 2 AWG
Wire size	Copper 60 °C	Copper 75 °C	Aluminum 60 °C	Aluminum 75 °C
14 AWG	15 A	15 A	—	—
12 AWG	20 A	20 A	15 A	15 A
10 AWG	30 A	30 A	25 A	25 A
8 AWG	40 A	50 A	35 A	40 A
6 AWG	50 A	60 A	40 A	50 A
4 AWG	70 A	80 A	50 A	60 A
3 AWG	80 A	100 A	60 A	70 A
2 AWG	90 A	110 A	70 A	90 A
1 AWG	110 A	125 A	80 A	100 A
1/0 AWG	125 A	150 A	100 A	110 A
2/0 AWG	125 A	175 A	110 A	125 A
3/0 AWG	150 A	200 A	125 A	150 A
4/0 AWG	175 A	225 A	150 A	175 A
250 kcmil	200 A	250 A	150 A	200 A
300 kcmil	225 A	250 A	175 A	225 A
350 kcmil	250 A	300 A	200 A	250 A
400 kcmil	250 A	300 A	225 A	250 A
500 kcmil	300 A	350 A	250 A	300 A
600 kcmil	350 A	400 A	250 A	300 A

Copper 60 °C
Copper 75 °C
Aluminum 60 °C
Aluminum 75 °C

Largest breaker by wire size.

How the breaker size chart works

Each value is the largest standard breaker that does not exceed the wire's ampacity, after the small-conductor limits for 14, 12 and 10 AWG. In some cases the code allows the next standard size up when the ampacity falls between two breaker sizes; this chart does not apply that allowance, so it errs on the safe side.

Motor circuits, air conditioners and other equipment with a nameplate maximum breaker follow their own rules: use the size printed on the nameplate.

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Sources

NFPA 70, National Electrical Code (2023): Allowable ampacities of insulated conductors, Table 310.16
NFPA 70, National Electrical Code (2023): Overcurrent protection of small conductors, Section 240.4(D)

Compared with 6 published documents, last on 2026-11-13

American Wire Group (edition not stated): Allowable Ampacities of Insulated Aluminum or Copper-Clad Aluminum Conductors — Aluminum columns and the 15/25 A aluminum small-conductor limits
Cerrowire (NEC 2017): Ampacity Charts — Copper 60/75/90 °C and aluminum 75/90 °C, 14 AWG to 600 kcmil
LugsDirect (NEC 2020): Ampacities of Insulated Conductors From NEC Table 310.16 — All columns, copper and aluminum, every size on this site
Omni Cable (NEC 2017): NEC Ampacity Data — All columns, copper and aluminum
Southwire (NEC 2023): SPEC 10003, THHN/THWN-2 building wire — 14–10 AWG copper and the 15/20/30 A small-conductor limits
Southwire (NEC 2023): SPEC 45007, aluminum XHHW-2 building wire — Copper small-conductor limits 15/20/30 A

Calculated by Calculate.diy with the method of the National Electrical Code® (NEC®), 2023 edition; not the NEC text. Methodology. For planning only: check local code and use a licensed electrician.