Ampacity Tables

Copper and aluminum conductor ampacity tables with derating and correction factors.

4 reference items · 3 sections

Copper Conductors Aluminum / Copper-Clad Aluminum Derating & Correction Factors

Copper Conductors

Copper Conductor Ampacity (60/75/90°C)

Allowable Ampacities — Copper Conductors

AWG/kcmil	60°C (TW, UF)	75°C (THW, THWN)	90°C (THHN, XHHW)
14	15	20	25
12	20	25	30
10	30	35	40
8	40	50	55
6	55	65	75
4	70	85	95
3	85	100	115
2	95	115	130
1	110	130	145
1/0	125	150	170
2/0	145	175	195
3/0	165	200	225
4/0	195	230	260
250	215	255	290
300	240	285	320
350	260	310	350
400	280	335	380
500	320	380	430
600	355	420	475
700	385	460	520
750	400	475	535
800	410	490	555
900	435	520	585
1000	455	545	615

1.Based on ambient temperature of 30°C (86°F)

2.Not more than 3 current-carrying conductors in raceway/cable

3.14 AWG: max 15A overcurrent protection

4.12 AWG: max 20A overcurrent protection

5.10 AWG: max 30A overcurrent protection

For ambient temperatures other than 30°C, apply temperature correction factors. For more than 3 current-carrying conductors, apply adjustment factors.

Aluminum / Copper-Clad Aluminum

Aluminum Conductor Ampacity (60/75/90°C)

NEC 310.16

Allowable Ampacities — Aluminum Conductors

AWG/kcmil	60°C (TW, UF)	75°C (THW, THWN)	90°C (THHN, XHHW)
12	15	20	25
10	25	30	35
8	30	40	45
6	40	50	60
4	55	65	75
3	65	75	85
2	75	90	100
1	85	100	115
1/0	100	120	135
2/0	115	135	150
3/0	130	155	175
4/0	150	180	205
250	170	205	230
300	190	230	255
350	210	250	280
400	225	270	305
500	260	310	350
600	285	340	385
700	310	375	420
750	320	385	435
800	330	395	450
900	355	425	480
1000	375	445	500

1.Based on ambient temperature of 30°C (86°F)

2.Not more than 3 current-carrying conductors in raceway/cable

3.Aluminum 12 AWG: max 15A overcurrent protection

Derating & Correction Factors

Temperature Correction Factors

NEC 310.15(B)

Ambient Temperature Correction Factors

Ambient °C	Ambient °F	60°C	75°C	90°C
21-25	70-77	1.08	1.05	1.04
26-30	79-86	1.00	1.00	1.00
31-35	88-95	0.91	0.94	0.96
36-40	97-104	0.82	0.88	0.91
41-45	106-113	0.71	0.82	0.87
46-50	115-122	0.58	0.75	0.82
51-55	124-131	0.41	0.67	0.76
56-60	133-140	—	0.58	0.71
61-65	142-149	—	0.47	0.65
66-70	151-158	—	0.33	0.58

1.Multiply the ampacity from the table by the correction factor

2.For ambient temps above 30°C, factors reduce ampacity

Example: 10 AWG THHN (90°C column = 40A) at 45°C ambient → 40 × 0.87 = 34.8A

Conduit Fill Adjustment Factors

NEC 310.15(C)(1)

Adjustment Factors for More Than 3 Current-Carrying Conductors

Conductors	Adjustment Factor
4-6	80%
7-9	70%
10-20	50%
21-30	45%
31-40	40%
41+	35%

1.Apply to ampacity from table — multiply ampacity by factor

2.Neutral conductors carrying only unbalanced current are not counted

3.Equipment grounding conductors are not counted

When both temperature correction AND conduit fill adjustment apply, multiply both factors together. Example: 10 AWG THHN at 40°C with 6 conductors → 40A × 0.91 × 0.80 = 29.1A

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