Wire Ampacity Chart

Complete ampacity calculations for all wire sizes per NEC 2023 Table 310.16. Each page shows the full derating sequence, not just the table value. Base ampacity temp correction bundling 110.14(C) termination limit.

Wire ampacity is the maximum current a conductor can carry continuously under stated conditions, per NEC Table 310.16. The "usable" ampacity shown below accounts for the 110.14(C) termination temperature limit that applies to most residential and commercial equipment. For each wire size, click through to see the full derating sequence with temperature correction and bundling adjustment applied.

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Copper THHN

THHN copper is rated 90C but usable ampacity is limited to the 75C column (or 60C for circuits 100A and under with 60C-rated equipment) per NEC 110.14(C).

Wire90°C75°C60°CUsable
14 AWG25A20A15A20A
12 AWG30A25A20A25A
10 AWG40A35A30A35A
8 AWG55A50A40A50A
6 AWG75A65A55A65A
4 AWG95A85A70A85A
3 AWG115A100A85A100A
2 AWG130A115A95A115A
1 AWG145A130A110A130A
1/0 AWG170A150A125A150A
2/0 AWG195A175A145A175A
3/0 AWG225A200A165A200A
4/0 AWG260A230A195A230A

Aluminum THHN

Wire90°C75°C60°CUsable
12 AWG25A20A15A20A
10 AWG35A30A25A30A
8 AWG45A40A35A40A
6 AWG55A50A40A50A
4 AWG75A65A55A65A
3 AWG85A75A65A75A
2 AWG100A90A75A90A
1 AWG115A100A85A100A
1/0 AWG135A120A100A120A
2/0 AWG150A135A115A135A
3/0 AWG175A155A130A155A
4/0 AWG205A180A150A180A

Copper XHHW-2

Wire90°C75°CUsable
14 AWG25A20A20A
12 AWG30A25A25A
10 AWG40A35A35A
8 AWG55A50A50A
6 AWG75A65A65A
4 AWG95A85A85A
3 AWG115A100A100A
2 AWG130A115A115A
1 AWG145A130A130A
1/0 AWG170A150A150A
2/0 AWG195A175A175A
3/0 AWG225A200A200A
4/0 AWG260A230A230A

Aluminum XHHW-2

Wire90°C75°CUsable
12 AWG25A20A20A
10 AWG35A30A30A
8 AWG45A40A40A
6 AWG55A50A50A
4 AWG75A65A65A
3 AWG85A75A75A
2 AWG100A90A90A
1 AWG115A100A100A
1/0 AWG135A120A120A
2/0 AWG150A135A135A
3/0 AWG175A155A155A
4/0 AWG205A180A180A

Copper NM-B (Romex)

Wire90°C60°CUsable
14 AWG25A15A15A
12 AWG30A20A20A
10 AWG40A30A30A
8 AWG55A40A40A
6 AWG75A55A55A
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Frequently Asked Questions

What is wire ampacity?

Ampacity is the maximum current (in amps) a conductor can carry continuously without exceeding its temperature rating. NEC Table 310.16 provides ampacity values for conductors in raceway or cable at 30C ambient. The usable ampacity depends on the insulation type, installation conditions, and termination temperature limits per 110.14(C).

What NEC table shows wire ampacity?

NEC Table 310.16 is the primary ampacity table for conductors in raceway, cable, or earth. Table 310.17 covers free-air installations. Table 310.12 covers dwelling service conductors. All tables are based on NEC 2023 (NFPA 70).

What is the ampacity of 12 AWG copper wire?

12 AWG copper THHN has a base ampacity of 30A at 90C per Table 310.16. After applying the 110.14(C) termination limit (75C for most equipment), the usable ampacity is 25A. For NM-B (Romex), the 60C outer jacket limit reduces it to 20A. See our 12 AWG ampacity page for full derating.

Does wire ampacity change with temperature?

Yes. NEC Table 310.16 assumes 30C (86F) ambient. Higher ambient temperatures reduce ampacity through correction factors from Table 310.15(B)(1). At 40C, a 75C-rated conductor retains 88% of its table ampacity. At 50C (common in attics), it retains only 75%. Use our ampacity calculator to apply temperature correction automatically.

What is the 110.14(C) termination limit?

NEC 110.14(C) limits the temperature rating you can use for ampacity calculations based on the equipment terminals. For circuits 100A or less, use the 60C column unless all terminations are rated 75C. For circuits over 100A, the 75C column applies. This is why 12 AWG THHN (rated 30A at 90C) is limited to 25A in practice.

Requirements vary by state. NEC edition, licensing, permits, and GFCI rules differ by jurisdiction. Check your state or pick it below for personalized info across WireRef.
Important: For reference only. Not a substitute for a licensed electrician. Electrical work can cause serious injury, death, fire, or property damage if performed incorrectly. Always hire a licensed electrician for electrical work, especially for service upgrades, panel work, and 240V circuits. Values are derived from NFPA 70 (NEC) for educational purposes. Always verify against your locally adopted NEC edition and amendments - local jurisdictions may enforce stricter requirements. WireRef provides reference information only and is not responsible for work performed based on this content. NEC® is a registered trademark of the National Fire Protection Association. Free NEC access via NFPA · OSHA Electrical Safety · Terms of use.

NEC 2023 references verified May 2026