Ampacity Chart

Amperage is a measure of the electrical current flowing through a circuit. Current is measured in amperes or “amps”. You must use the correct size wire for the amperage requirement of the circuit to prevent the wire from over heating.

The number and type of electrical devices connected to a circuit determine the amperage requirement of the circuit. Usually, a general purpose house circuit is designed for 20 amps. Lighting circuits may be designed for only 15 amps.

To calculate the amperage for a circuit, first add up the wattage of all the electrical devices that will be on the circuit. Then, divide the total wattage by the voltage of the system, 110 or 220, and that will give you the expected current or amps.

Copper Aluminum
  60°C (140°F) 75°C (167°F) 90°C (194°F) 75°C (167°F) 90°C (194°F)
Wire Guage Size NM-B, UF-B THW, THWN,
SE, USE, XHHW
THWN-2, THHN,
XHHW-2, USE-2
THW, THWN,
SE, USE, XHHW
XHHW-2, THHN,
THWN-2
14 15 15 15 - -
12 20 20 20 15 15
10 30 30 30 25 25
8 40 50 55 40 45
6 55 65 75 50 60
4 70 85 95 65 75
3 85 100 110 75 85
2 95 115 130 90 100
1 - 130 150 100 115
1/0 - 150 170 120 135
2/0 - 175 195 135 150
3/0 - 200 225 155 175
4/0 - 230 260 180 205
250 - 255 290 205 230
300 - 285 320 230 255
350 - 310 350 250 280
500 - 380 430 310 350
600 - 420 475 340 385
750 - 475 535 385 435
1000 - 545 615 445 500
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