Online Calculators and Tables to Help You Determine Proper Wire Size


Electrical current is measured in amps. Each wire size, or wire gauge (AWG), has a maximum current limit that a wire can handle before damage occurs. It is important to pick the correct size of wire so that the wire doesn't overheat.

The number of devices connected to the circuit usually determines how much current will flow through the wire.

The wire size chart below shows allowable ampacities of insulated conductors rated up to and including 2000 Volts, 60°C through 90°C (140°F through 194°F), not more than three current-carrying conductors in raceway, cable, or earth (directly buried), based on ambient air temperature of 30°C (86°F).

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Wire Size Chart and Maximum Amp Ratings

Source: NFPA 70, National Electrical Code, Table 310.15(B)(16)
SIZE 60°C
(140°F)		 75°C
(167°F)		 90°C
(194°F)		 60°C
(140°F)		 75°C
(167°F)		 90°C
(194°F)		 SIZE
AWG
or
kcmil		 TYPES
TW,
UF		 TYPES
RHW,
THW,
THWN		 TYPES
TBS,
SA,
SIS		 TYPES
TW,
UF		 TYPES
RHW,
THW,
THWN		 TYPES
TBS,
SA,
SIS		 AWG
or
kcmil
COPPER ALUMINUM
14 20 20 25 - - - 14
12 25 25 30 20 20 25 12
10 30 35 40 25 30 35 10
8 40 50 55 30 40 45 8
6 55 65 75 40 50 60 6
4 70 85 95 55 65 75 4
3 85 100 110 65 75 85 3
2 95 115 130 75 90 100 2
1 110 130 150 85 100 115 1
1/0 125 150 170 100 120 135 1/0
2/0 145 175 195 115 135 150 2/0
3/0 165 200 225 130 155 175 3/0
4/0 195 230 260 150 180 205 4/0
250 215 255 290 170 205 230 250
300 240 285 320 190 230 255 300
350 260 310 350 210 250 280 350
400 280 335 380 225 270 305 400
500 320 380 430 260 310 350 500
600 355 420 475 285 340 385 600
700 385 460 520 310 375 420 700
750 400 475 535 320 385 435 750
800 410 490 555 330 395 450 800
900 435 520 585 355 425 480 900
1000 455 545 615 375 445 500 1000
1250 495 590 665 405 485 545 1250
1500 520 625 705 435 520 585 1500
1750 545 650 735 455 545 615 1750
2000 560 665 750 470 560 630 2000

Note: View additional wire size charts from the list below.

Maximum Allowable Ampacities for Conductors in Free Air (30°C) Maximum Allowable Ampacities for Conductors in Raceway, Cable or Earth (40°C) Maximum Allowable Ampacities for Conductors in Free Air (40°C)

For ambient temperatures other than 30°C, Correction Factors must be taken into consideration.


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