Copper Conductor Ampacity Table

NEC 2023Every value in this table is transcribed from the 2023 NEC (NFPA 70, 2023). The code is republished on a three-year cycle and adoption varies by jurisdiction - confirm against your locally adopted edition and your authority having jurisdiction (AHJ) before you build.

Allowable ampacity of insulated copper conductors rated up to 2000 V, with not more than three current-carrying conductors in a raceway, cable, or earth, based on an ambient temperature of 30°C (86°F). The final column is the separate small-conductor overcurrent ceiling, which applies regardless of the ampacity shown.
Size	60°C	75°C	90°C	Overcurrent cap
14 AWG	15	20	25	15 A
12 AWG	20	25	30	20 A
10 AWG	30	35	40	30 A
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	-

Source: NFPA 70, National Electrical Code, Table 310.16; NFPA 70, National Electrical Code, 240.4(D). Published by NFPA.NEC 2023Transcribed from the 2023 NEC (NFPA 70, 2023). Confirm against your locally adopted edition and your authority having jurisdiction (AHJ).

Reading this table

The three temperature columns are the conductor's insulation rating, not the ambient temperature. A 90°C-rated conductor is not permitted to run hotter than the equipment it terminates on allows - and most breakers and equipment are listed for 60°C or 75°C. In practice the 75°C column governs most installations, and the 90°C column is used as the starting point for derating rather than as a final ampacity.

The overcurrent cap column

The smallest conductors carry a fixed protection ceiling that is separate from ampacity. It exists because small conductors have little thermal mass and are easily damaged, and it applies regardless of what the temperature columns read. The cited section carries specific exceptions this table does not reproduce.

Before you use these numbers

Correct for ambient temperature and adjust for the number of current-carrying conductors before sizing anything - see the temperature correction and bundling adjustment tables, or let the ampacity lookup apply both.

Aluminum ampacity Temperature correction Bundling adjustment Breaker sizes Grounding conductors Conduit fill Conductor properties

FAQ

Frequently asked questions

Which temperature column should I use?

The three temperature columns are the conductor's insulation rating, not the ambient temperature, and a conductor is not permitted to run hotter than the equipment it terminates on allows. Most breakers and equipment are listed for 60°C or 75°C, so in practice the 75°C column governs most installations and the 90°C column is used as the starting point for derating rather than as a final ampacity.

Does the 80 percent rule apply to these ampacities?

Not to the table values themselves - they are allowable ampacities at a 30°C ambient with no more than three current-carrying conductors. Continuous loading is handled separately: a load that runs three hours or more is sized at 125 percent, which is the same arithmetic as loading the circuit to 80 percent. The smallest conductors also carry a fixed overcurrent cap that applies regardless of what the temperature columns read.

When does aluminum need upsizing?

Whenever a run planned in copper is switched to aluminum. Compared with copper of the same size, aluminum carries less current and has higher resistance, so aluminum runs need larger conductors and drop more voltage over the same distance - see the aluminum table for the reduced ratings.