What wire size do I need for each breaker?

15 A takes 14 AWG copper, 20 A takes 12 AWG, 30 A takes 10 AWG, 40 A takes 8 AWG, 50 A and 60 A take 6 AWG, 100 A takes 1 AWG, and 200 A takes 4/0. Aluminum needs roughly two gauge sizes larger for the same rating.

Can I put a bigger breaker on my existing wire?

No. The breaker protects the wire, not the appliance. Installing a larger breaker on existing conductors removes that protection and is one of the most common causes of electrical fires. If a breaker trips repeatedly, the fix is a load calculation and possibly a new circuit — never a larger breaker on the same wire.

Why is the maximum load only 80% of the breaker rating?

That applies to continuous loads — those running three hours or more. NEC 210.20(A) requires the overcurrent device to be rated at 125% of a continuous load, which is the same as limiting the continuous load to 80% of the breaker. Non-continuous loads may use the full rating.

What size ground wire goes with each breaker?

From NEC Table 250.122: 14 AWG copper for 15 A, 12 AWG for 20 A, 10 AWG for anything up to 60 A, 8 AWG up to 100 A, and 6 AWG up to 200 A. The table gives maximum device ratings, so you round up to the next listed row.

Circuit Breaker Size Chart

What wire size does each breaker need, what ground wire goes with it, and how much load it can actually carry. Conductor sizes follow the 75°C column of NEC Table 310.16; grounds follow NEC Table 250.122.

Breaker	Copper	Aluminum	Ground (Cu)	Max continuous	Poles	Typical use
15A	14 AWG	12 AWG	14 AWG	12 A	Single-pole	General lighting circuits
20A	12 AWG	10 AWG	12 AWG	16 A	Single-pole	Kitchen small-appliance circuits
30A	10 AWG	8 AWG	10 AWG	24 A	Double-pole	Electric clothes dryers
40A	8 AWG	6 AWG	10 AWG	32 A	Double-pole	Electric ranges and cooktops
50A	6 AWG	4 AWG	10 AWG	40 A	Double-pole	Electric ranges
60A	6 AWG	4 AWG	10 AWG	48 A	Double-pole	Sub-panels
100A	1 AWG	1/0 AWG	8 AWG	80 A	Double-pole	Main service for a small home
200A	4/0 AWG	4/0 AWG	6 AWG	160 A	Double-pole	Standard main service for a modern single-family home

Maximum continuous load is 80% of the breaker rating, the inverse of the 125% sizing requirement in NEC 210.20(A). Non-continuous loads may use the full breaker rating.

Breaker Sizes

15 Amp Breaker

14 AWG copper · single-pole · 120 V

20 Amp Breaker

12 AWG copper · single-pole · 120 V

30 Amp Breaker

10 AWG copper · double-pole · 240 V or 120 V

40 Amp Breaker

8 AWG copper · double-pole · 240 V

50 Amp Breaker

6 AWG copper · double-pole · 240 V

60 Amp Breaker

6 AWG copper · double-pole · 240 V

100 Amp Breaker

1 AWG copper · double-pole · 240 V

200 Amp Breaker

4/0 AWG copper · double-pole · 240 V

The breaker protects the wire

This is the single idea behind every number on this page. A circuit breaker exists to open the circuit before the conductor overheats. It is chosen to match the wire, not the appliance. An appliance that trips a correctly sized breaker is drawing more than the circuit was built for — the answer is a bigger circuit, never a bigger breaker on the same wire.

Three code rules set the ceiling, and the smallest one wins. Table 310.16 gives the conductor ampacity. NEC 240.4(D) caps 14, 12 and 10 AWG copper at 15, 20 and 30 A regardless of what the table says. NEC 110.14(C) limits you to the termination temperature rating, normally 75°C, even when the conductor is 90°C THHN.

Then two more can pull the required conductor larger: 310.15 derating for hot ambients or crowded raceways, and voltage drop on long runs.

Wire size by amperage → NEC Table 250.122 — ground wire size → NEC Table 310.16 — conductor ampacity → Appliance wiring guides → Wire size calculator →

Circuit Breaker Size Chart

Breaker Sizes

The breaker protects the wire

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