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).

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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).

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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.

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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.

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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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