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Wire & breaker size chart

NEC wire gauge and breaker sizing at a glance: the right breaker and copper wire for common loads, plus conductor ampacity by AWG.

Breaker & wire by common load

BreakerNM-B cable (Romex)Conduit / SER (75°C)Typical use
15 A14 AWG14 AWGLighting, general outlets
20 A12 AWG12 AWGKitchen, bath, garage outlets
30 A10 AWG10 AWGElectric dryer, water heater
40 A8 AWG8 AWGElectric range, 32A EV charger
50 A6 AWG8 AWGRange, 40A EV charger, NEMA 14-50
60 A4 AWG6 AWG48A EV charger, subpanel feed
70 A–4 AWGLarge subpanel, heat pump
80 A–4 AWGSubpanel, 64A EV charging
90 A–3 AWGSubpanel feeder
100 A–3 AWGSubpanel, small service
125 A–1 AWGLarge subpanel
200 A–2/0 AWGMain dwelling service (NEC 310.12)

Two columns because the wiring method decides the answer. Most residential branch circuits are NM-B cable, and NEC 334.80 requires NM cable ampacity to be taken from the 60°C column even though the conductors carry 90°C insulation, which forces a larger conductor at 50 A and above. Runs in conduit (THHN/THWN-2) or SER cable use the 75°C column, assuming 75°C-rated terminations (NEC 110.14(C)). A dash means NM-B is not normally used at that size.

Branch circuit wire size chart: minimum copper conductor for 15, 20, 30, 40, 50 and 60 amp breakers, comparing NM-B cable sizes from the NEC 60°C column with conduit sizes from the 75°C column. NM-B needs one size larger at 50 A and 60 A.
Branch circuits, 15–60 A. NM-B (NEC 334.80) vs conduit (NEC 310.16, 75°C column).
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<a href="https://wattsimple.com/reference/wire-breaker-size"><img src="https://wattsimple.com/charts/wire-breaker-size.svg" alt="Wire size chart for 15 to 60 amp breakers" width="1200" height="652" style="max-width:100%;height:auto" loading="lazy"></a> <p style="font:14px/1.5 system-ui,sans-serif;margin:8px 0 0">Chart: <a href="https://wattsimple.com/reference/wire-breaker-size">WattSimple</a></p>
Feeder and service wire size chart: minimum 75°C copper conductor for 70 through 200 amp feeders, with each conductor's ampacity from NEC Table 310.16. The 200 A dwelling service uses 2/0 copper under the 83% allowance of NEC 310.12.
Feeders and services, 70–200 A: conduit or SER, where NM-B no longer applies.
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<a href="https://wattsimple.com/reference/wire-breaker-size"><img src="https://wattsimple.com/charts/feeder-wire-size.svg" alt="Feeder and service wire size chart, 70 to 200 amps" width="1200" height="652" style="max-width:100%;height:auto" loading="lazy"></a> <p style="font:14px/1.5 system-ui,sans-serif;margin:8px 0 0">Chart: <a href="https://wattsimple.com/reference/wire-breaker-size">WattSimple</a></p>

Copper conductor ampacity (NEC 310.16)

Wire (AWG)60°C75°C90°CMax breaker
14 AWG15 A20 A25 A15 A
12 AWG20 A25 A30 A20 A
10 AWG30 A35 A40 A30 A
8 AWG40 A50 A55 A–
6 AWG55 A65 A75 A–
4 AWG70 A85 A95 A–
3 AWG85 A100 A115 A–
2 AWG95 A115 A130 A–
1 AWG110 A130 A145 A–
1/0 AWG125 A150 A170 A–
2/0 AWG145 A175 A195 A–
3/0 AWG165 A200 A225 A–
4/0 AWG195 A230 A260 A–

How sizing works

  • Continuous loads (such as EV charging) require the circuit and overcurrent device at 125% of the load: NEC 625.41 and 210.20(A).
  • Wire here assumes 75°C-rated terminations per NEC 110.14(C). 60°C terminations, long runs (voltage drop), or aluminum conductors need upsizing.
  • 14, 12, and 10 AWG have small-conductor overcurrent limits under NEC 240.4(D): see the Max breaker column.
  • Always confirm sizing with a licensed electrician and your local authority having jurisdiction (AHJ).

Test before you touch

Before working on any circuit sized from this chart, confirm it is dead with a voltage pen. A clamp meter reads the real load on one conductor, which shows how close an existing circuit runs to its breaker. Panel work is for someone qualified, under a permit where your AHJ requires one.

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