Every breaker,
its wire.

A sheet for each common breaker size from 15 to 200 amps. Each gives the copper NM-B, copper THHN and aluminum sizes with ampacity at least the breaker rating, the Table 250.122 ground, the longest run at 3 percent drop, the 125 percent continuous-load limit and, at 100 A and up, the 83 percent rule for a house service.

Wire size for 15 to 200 amp breakers: copper NM-B at 60 °C, copper THHN and aluminum at 75 °C, copper ground and the longest 240 V run at 3 % drop on 80 % load
Breaker	Cu NM-B	Cu THHN	Aluminum	Ground	240 V run
15 A	14 AWG	14 AWG	12 AWG	14 AWG	95 ft
20 A	12 AWG	12 AWG	10 AWG	12 AWG	113 ft
30 A	10 AWG	10 AWG	8 AWG	10 AWG	120 ft
40 A	8 AWG	8 AWG	8 AWG	10 AWG	144 ft
50 A	6 AWG	8 AWG	6 AWG	10 AWG	115 ft
60 A	4 AWG	6 AWG	4 AWG	10 AWG	152 ft
70 A	4 AWG	4 AWG	3 AWG	8 AWG	208 ft
80 A	3 AWG	4 AWG	2 AWG	8 AWG	182 ft
100 A	—	3 AWG	1 AWG	8 AWG	183 ft
200 A	—	3/0 AWG	250 kcmil	6 AWG	293 ft

NM-B is made only up to 2 AWG copper. Runs are one way at 80 % of the breaker rating.

Every breaker,its wire.

Browse all 20 gauges, 12 conduit sizes and 10 circuits

Every breaker,
its wire.