Wire Ampacity Calculator

Calculate the maximum allowable wire ampacity for an insulated conductor given its gauge, material, temperature rating, ambient temperature, and conductor count.

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Wire Ampacity Rating:

15 A
Ampacity rating as given by NEC Table 310.16 with temperature correction factor applied using Table 310.15(B)(1) and current carrying conductor adjustment factor applied using Table 310.15(C)(1).
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Joe is the creator of Inch Calculator and has over 20 years of experience in engineering and construction. He holds several degrees and certifications.

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How to Calculate the Wire Ampacity Rating

You can calculate the ampacity rating of a wire or conductor by referencing the chart indicating the allowable wire ampacities of insulated conductors that is provided by the National Electric Code.

The wire ampacity rating chart provided by the NEC (see below) is used in conjunction with the ambient temperature rating correction factor and the current carrying conductor adjustment factor charts also provided by the NEC (also below) to calculate the ampacity rating of a wire.

Wire Ampacity Chart

Chart showing the allowable wire ampacities of insulated conductors per NEC Table 310.16.
Wire Gauge Copper Aluminum
60 °C 75 °C 90 °C 60 °C 75 °C 90 °C
18 AWG — — 14 — — —
16 AWG — — 18 — — —
14 AWG 15 20 25 — — —
12 AWG 20 25 30 15 20 25
10 AWG 30 35 40 25 30 35
8 AWG 40 50 55 35 40 45
6 AWG 55 65 75 40 50 55
4 AWG 70 85 95 55 65 75
3 AWG 85 100 115 65 75 85
2 AWG 95 115 130 75 90 100
1 AWG 110 130 145 85 100 115
0 (1/0) AWG 125 150 170 100 120 135
00 (2/0) AWG 145 175 195 115 135 150
000 (3/0) AWG 165 200 225 130 155 175
0000 (4/0) AWG 195 230 260 150 180 205
250 kcmil 215 255 290 170 205 230
300 kcmil 240 285 320 195 230 260
350 kcmil 260 310 350 210 250 280
400 kcmil 280 335 380 225 270 305
500 kcmil 320 380 430 260 310 350
600 kcmil 350 420 475 285 340 385
700 kcmil 385 460 520 315 375 425
750 kcmil 400 475 535 320 385 435
800 kcmil 410 490 555 330 395 445
900 kcmil 435 520 585 355 425 480
1000 kcmil 455 545 615 375 445 500
1250 kcmil 495 590 665 405 485 545
1500 kcmil 525 625 705 435 520 585
1750 kcmil 545 650 735 455 545 615
2000 kcmil 555 665 750 470 560 630

Ambient Temperature Correction Factors

Wire ampacity ambient temperature correction factors per NEC Table 310.15(B)(1).
Ambient Temperature Conductor Temperature Rating
60 °C 75 °C 90 °C
<= 50 °F (<= 10 °C) 1.29 1.20 1.15
51-59 °F (11-15 °C) 1.22 1.15 1.12
60-68 °F (16-20 °C) 1.15 1.11 1.08
69-77 °F (21-25 °C) 1.08 1.05 1.04
78-86 °F (26-30 °C) 1.00 1.00 1.00
87-95 °F (31-35 °C) 0.91 0.94 0.96
96-104 °F (36-40 °C) 0.82 0.88 0.91
105-113 °F (41-45 °C) 0.71 0.82 0.87
114-122 °F (46-50 °C) 0.58 0.75 0.82
123-131 °F (51-55 °C) 0.41 0.67 0.76
132-140 °F (56-60 °C) — 0.58 0.71
141-149 °F (61-65 °C) — 0.47 0.65
150-158 °F (66-70 °C) — 0.33 0.58
159-167 °F (71-75 °C) — — 0.50
168-176 °F (76-80 °C) — — 0.41
177-185 °F (81-85 °C) — — 0.29

Current Carrying Conductor Adjustment Factors

Wire ampacity current carrying conductor adjustment factors per NEC Table 310.15(C)(1).
Number of Conductors in Raceway or Cable Wire Ampacity Adjustment Factor
1-3 1.00
4-6 0.80
7-9 0.70
10-20 0.50
21-30 0.45
31-40 0.40
41 or more 0.35

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