Wire Ampacity Chart
Allowable ampacity of copper and aluminum building wire by size and temperature rating, with a calculator that applies ambient-temperature and conductor-count derating for you.
Copper at 75°C: 14 AWG = 20 A (15 A breaker), 12 AWG = 25 A (20 A breaker), 10 AWG = 35 A (30 A breaker), 8 AWG = 50 A, 6 AWG = 65 A, 4 AWG = 85 A, 2 AWG = 115 A, 1/0 = 150 A, 4/0 = 230 A.
| Copper | Aluminum or copper-clad aluminum | |||||
|---|---|---|---|---|---|---|
| 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 |
| 350 kcmil | 260 | 310 | 350 | 210 | 250 | 280 |
| 500 kcmil | 320 | 380 | 430 | 260 | 310 | 350 |
Sizes 18 AWG to 2000 kcmil are on the full Table 310.16 page.
Ampacity & derating calculator
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Ampacity tables
Raceway, Cable or Earth
Not more than three current-carrying conductors in a raceway, cable or directly buried, 30°C (86°F) ambient.
Table 310.17Single Conductors in Free Air
Single insulated conductors spaced apart in free air, 30°C (86°F) ambient.
Table 310.18High-Temperature, in Raceway or Cable
Conductors rated 150°C, 200°C and 250°C, not more than three in a raceway or cable, 40°C (104°F) ambient..
Table 310.19High-Temperature, in Free Air
Single conductors rated 150°C, 200°C and 250°C in free air, 40°C (104°F) ambient..
310.15(B) · 310.15(C)Derating factors
Ambient temperature correction and adjustment for more than three current-carrying conductors.
Choosing the right column
| Column | Conductor types |
|---|---|
| 60°C (140°F) | TW, UF |
| 75°C (167°F) | RHW, THHW, THW, THWN, XHHW, USE, ZW |
| 90°C (194°F) | TBS, SA, SIS, FEP, FEPB, MI, RHH, RHW-2, THHN, THHW, THW-2, THWN-2, USE-2, XHH, XHHW, XHHW-2, ZW-2 |
A conductor’s ampacity is the current it can carry continuously without exceeding its insulation temperature rating. Three things change it: the insulation rating, the surrounding (ambient) temperature, and how many loaded conductors share the raceway and heat each other.
The weakest link governs. THHN is a 90°C wire, but if it lands on a 75°C breaker lug it may only be loaded to the 75°C value; the 90°C figure is still useful because derating factors are applied to it first.
Small conductors: regardless of the table, overcurrent protection may not exceed 15 A for 14 AWG, 20 A for 12 AWG and 30 A for 10 AWG copper (15 A and 25 A for 12 and 10 AWG aluminum), with specific exceptions such as motor and HVAC circuits.
Continuous loads: size conductors and breakers at 125% of any load expected to run three hours or more.
Frequently asked questions
Which ampacity column should I use — 60, 75 or 90°C?
Use the column for the lowest-rated part of the circuit. Breakers, panels and most equipment are rated 75°C, so 75°C is the normal answer. Equipment rated 100 A or less, or marked for 14–1 AWG, is treated as 60°C unless it is marked 75°C. NM-B cable is limited to the 60°C column by 334.80. The 90°C column is used only as the starting point for derating.
What is the ampacity of 12 gauge wire?
12 AWG copper is 20 A at 60°C, 25 A at 75°C and 30 A at 90°C, but 240.4(D) limits its overcurrent protection to 20 A in almost all cases. 12 AWG aluminum is 15, 20 and 25 A with a 15 A limit.
What size wire do I need for 100 amps?
3 AWG copper or 1 AWG aluminum at 75°C terminations. For a 100 A dwelling service or main feeder, 310.12 permits 4 AWG copper or 2 AWG aluminum.
What size wire for a 200 amp service?
For a dwelling, 2/0 AWG copper or 4/0 AWG aluminum under the 83% rule of 310.12. For other 200 A feeders, 3/0 AWG copper or 250 kcmil aluminum from the 75°C column.
Did the ampacity table number change?
Yes. The 2020 NEC renumbered Table 310.15(B)(16) back to Table 310.16, and 310.15(B)(17) to 310.17. The values did not change.
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