Wire Ampacity Chart: NEC Table 310.16 (Cu & Al)

Wire Ampacity Chart

Allowable ampacity of copper and aluminum building wire from NEC Table 310.16: not more than three current-carrying conductors in raceway, cable or earth, at 30 °C ambient.

Size	Copper (A)			Aluminum (A)
Size	60 °C	75 °C	90 °C	60 °C	75 °C	90 °C
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
1/0 AWG	125	150	170	100	120	135
2/0 AWG	145	175	195	115	135	150
3/0 AWG	165	200	225	130	155	175
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
750 kcmil	400	475	535	320	385	435
1000 kcmil	455	545	615	375	445	500

* Overcurrent protection limited by NEC 240.4(D): 14 Cu 15 A, 12 Cu 20 A, 10 Cu 30 A, 12 Al 15 A, 10 Al 25 A. 60 °C: TW, UF. 75 °C: THW, THWN, XHHW, USE. 90 °C: THHN, THWN-2, XHHW-2, RHW-2.

How to read the chart

Pick the row for your conductor size, then the column for the material and the temperature rating you are allowed to use. The rating you can use is the lowest of three things: the wire's insulation rating, the termination rating on the breaker, and the termination rating on the equipment. THHN is a 90 °C wire, but on a breaker marked 75 °C you must use the 75 °C column for the final ampacity.

Worked examples

1. A 60 A subpanel feeder

With 75 °C terminations on both ends, 6 AWG copper is 65 A, enough for 60 A. In aluminum, 4 AWG is 65 A. If either end is only rated 60 °C, 6 AWG copper drops to 55 A and you would need 4 AWG copper (70 A).

2. Derating with the 90 °C column

Nine current-carrying 12 AWG THHN conductors share one conduit. Start at 30 A (90 °C). Seven to nine current-carrying conductors take a 70% adjustment: 30 × 0.70 = 21 A. That is still at least 20 A, and the 75 °C limit is 25 A, so each conductor can stay on a 20 A breaker. The ampacity derating calculator applies both temperature and fill factors.

3. An EV charger

A 48 A charger is a continuous load, so the circuit needs 48 × 1.25 = 60 A. 6 AWG copper at 75 °C (65 A) on a 60 A breaker works. The wire size calculator also checks voltage drop on the run.

Copper vs aluminum

Aluminum carries roughly 75–85% of the current of the same size of copper in Table 310.16 and is commonly used for feeders 1 AWG and larger because it is lighter and cheaper. Use terminals marked AL/CU, apply antioxidant where the manufacturer requires it, and torque connections to the specified value.

When this table does not apply

More than three current-carrying conductors or ambient above 30 °C: apply NEC 310.15(B) and 310.15(C)(1).
Single conductors in free air: Table 310.17.
Dwelling services and main feeders: Table 310.12 may be used.
Motor circuits: Article 430 uses 125% of table FLC.
Canada: use CEC Table 2 (copper) and Table 4 (aluminum); values are similar but not identical.

Ampacity and voltage drop are separate checks

A wire can have plenty of ampacity and still deliver too little voltage at the end of a long run. 12 AWG is fine for 16 A thermally, but at 150 ft on 120 V it drops more than 7%. Always check the run in the voltage drop calculator.

Frequently asked questions

What is wire ampacity?

The maximum current, in amperes, a conductor can carry continuously under its conditions of use without exceeding its insulation temperature rating (NEC Article 100).

Which column should I use, 60, 75 or 90 °C?

Use the lowest temperature rating of the conductor and every termination it connects to (NEC 110.14(C)). Equipment rated 100 A or less, or for 14–1 AWG, is assumed 60 °C unless marked 75 °C. Most modern breakers are marked 60/75 °C. The 90 °C column is for derating calculations with THHN or XHHW-2.

Why is 12 AWG listed at 25 A but only allowed on a 20 A breaker?

NEC 240.4(D) limits overcurrent protection for small conductors: 14 AWG copper to 15 A, 12 AWG to 20 A and 10 AWG to 30 A, whatever the table says. Sizes marked * in the chart are affected.

What ampacity is 6 AWG copper?

55 A at 60 °C, 65 A at 75 °C and 75 A at 90 °C. With 75 °C terminations it is suitable for a 60 A breaker.

What wire size for 200 amps?

By Table 310.16 at 75 °C: 3/0 copper (200 A) or 250 kcmil aluminum (205 A). For a dwelling service or main feeder, NEC 310.12 allows 2/0 copper or 4/0 aluminum.