National Electrical Code® Allowable Copper Conductor Ampacities

Ampacity Chart

From the 2017 Edition of the National Electrical Code® (NEC) NFPA70®

Table 310.15(B)(16)
Table 310.15(B)(17)
Table 310.15(B)(3)(a)
Table 310.15(B)(2)(a)

 

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Table 310.15(B)(16)

(formerly Table 310.16)

Allowable ampacities of insulated copper 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 temperature of 30°C (86°F).

Size Temperature Rating of Copper Conductor
(AWG or kcmil) 60°C (140°F) 75°C (167°F) 90°C (194°F)
18 AWG 14
16 AWG 18
14 AWG*   20 25
12 AWG*   25 30
10 AWG* 30 35 40
8 AWG 40 50 55
6 AWG 55 65 75
4 AWG 70 85 95
3 AWG 85 100 115
2 AWG 95 115 130
1 AWG 110 130 145
1/0 AWG 125 150 170
2/0 AWG 145 175 195
3/0 AWG 165 200 225
4/0 AWG 195 230 260
250 KCMIL 215 255 290
300 KCMIL 240 285 320
350 KCMIL 260 310 350
400 KCMIL 280 335 380
500 KCMIL 320 380 430
600 KCMIL 350 420 475
700 KCMIL 385 460 520
750 KCMIL 400 475 535
800 KCMIL 410 490 555
900 KCMIL 435 520 585
1000 KCMIL 455 545 615
1250 KCMIL 495 590 665
1500 KCMIL 525 625 705
1750 KCMIL 545 650 735
2000 KCMIL 555 665 750

Types

  • 60°C (140°F): TW, UF
  • 75°C (167°F): RHW, THHW, THW, THWN, XHHW, USE, ZW
  • 90°C (194°F): FEP, FEPB, MI, RHH, RHW-2, SA, SIS, TBS, THHN, THHW, THW-2, THWN-2, USE-2, XHH, XHHW, XHHW-2, ZW-2

Table 310.15(B)(17)

(formerly Table 310.17)

Allowable ampacities of single insulated copper conductors rated up to and including 2000 Volts in free air, based on ambient temperature of 30°C (86°F).

Size Temperature Rating of Copper Conductor
(AWG or kcmil) 60°C (140°F) 75°C (167°F) 90°C (194°F)
18 AWG 18
16 AWG 24
14 AWG*   30 35
12 AWG*   35 40
10 AWG*   50 55
8 AWG 60 70 80
6 AWG 80 95 105
4 AWG 105 125 140
3 AWG 120 145 165
2 AWG 140 170 190
1 AWG 165 195 220
1/0 AWG 195 230 260
2/0 AWG 225 265 300
3/0 AWG 260 310 350
4/0 AWG 300 360 405
250 KCMIL 340 405 455
300 KCMIL 375 445 500
350 KCMIL 420 505 570
400 KCMIL 455 545 615
500 KCMIL 515 620 700
600 KCMIL 575 690 780
700 KCMIL 630 755 850
750 KCMIL 655 785 885
800 KCMIL 680 815 920
900 KCMIL 730 870 980
1000 KCMIL 780 935 1055
1250 KCMIL 890 1065 1200
1500 KCMIL 980 1175 1325
1750 KCMIL 1070 1280 1445
2000 KCMIL 1155 1385 1560

Types

  • 60°C (140°F): TW, UF
  • 75°C (167°F): RHW, THHW, THW, THWN, XHHW, ZW
  • 90°C (194°F): FEP, FEPB, MI, RHH, RHW-2, SA, SIS, TBS, THHN, THHW, THW-2, THWN-2, USE-2, XHH, XHHW, XHHW-2, ZW-2

* Unless otherwise specifically permitted elsewhere in the NEC NFPA70 Code, the overcurrent protection for conductor types marked with an asterisk shall not exceed 15A for No. 14 copper, 20A for No. 12 copper, and 30A for No. 10 copper, after any correction factors for ambient temperature and number of conductors have been applied.


 

Table 310.15(B)(3)(a)

Adjustment factors for more than three current-carrying conductors in a raceway or cable.

Where the number of current-carrying conductors in a raceway or cable exceeds 3, the allowable ampacities shall be reduced per the table below.

Number of current-carrying conductors* Percent of values in tables as adjusted for ambient temperature (if necessary)
4 - 6 80
7 - 9 70
10 - 20 50
21 - 30 45
31 - 40 40
41 and more 35

* Does NOT include ground


 

Table 310.15(B)(2)(a)

Temperature Correction Factors

For ambient temperatures other than 30°C (86°F), multiply the allowable ampacities shown above by the appropriate factor shown per the table below.

Ambient Temperature 60°C (140°F) 75°C
(167°F)
90°C
(194°F)
50°F or less 10°C or less 1.29 1.20 1.15
51-59°F 11 to 15°C 1.22 1.15 1.12
60-68°F 16 to 20°C 1.15 1.11 1.08
69-77°F 21 to 25°C 1.08 1.05 1.04
78-86°F 26 to 30°C 1.00 1.00 1.00
87-95°F 31 to 35°C 0.91 0.94 0.96
96-104°F 36 to 40°C 0.82 0.88 0.91
105-113°F 41 to 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

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