Wire Ampacity Chart: NEC Table 310.16 Copper and Aluminum at 60, 75 and 90 C, Termination Rules, Temperature Correction and Bundling Derating
Sep 10, 2026
Summary: Conductor ampacity comes from NEC Table 310.16 (formerly 310.15(B)(16)) for up to three current-carrying conductors in a raceway or cable at 30 C ambient. Copper at 75 C: 14 AWG 20 A, 12 AWG 25 A, 10 AWG 35 A, 8 AWG 50 A, 6 AWG 65 A, 4 AWG 85 A, 3 AWG 100 A, 2 AWG 115 A, 1 AWG 130 A, 1/0 150 A, 2/0 175 A, 3/0 200 A, 4/0 230 A, 250 kcmil 255 A, 300 kcmil 285 A, 350 kcmil 310 A, 400 kcmil 335 A, 500 kcmil 380 A, 600 kcmil 420 A, 750 kcmil 475 A, 1000 kcmil 545 A. Aluminum at 75 C is roughly 78 percent of copper: 6 AWG 50 A, 4 AWG 65 A, 2 AWG 90 A, 1/0 120 A, 2/0 135 A, 4/0 180 A, 250 kcmil 205 A, 350 kcmil 250 A, 500 kcmil 310 A, 750 kcmil 385 A. The 75 C column governs almost every installation because NEC 110.14(C) limits ampacity to the temperature rating of the terminals, and lugs and breakers are rated 75 C; the 90 C column is used only as the starting point for derating. 240.4(D) caps 14 AWG copper at 15 A, 12 AWG at 20 A and 10 AWG at 30 A overcurrent protection regardless of the table.
Table 310.16, three or fewer conductors, 30 C ambient
| Size | Cu 60 C (TW, UF) | Cu 75 C (THWN, THHW, XHHW, USE) | Cu 90 C (THHN, THWN-2, XHHW-2) | Al 60 C | Al 75 C | Al 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 | 125 | 150 | 170 | 100 | 120 | 135 |
| 2/0 | 145 | 175 | 195 | 115 | 135 | 150 |
| 3/0 | 165 | 200 | 225 | 130 | 155 | 175 |
| 4/0 | 195 | 230 | 260 | 150 | 180 | 205 |
| 250 kcmil | 215 | 255 | 290 | 170 | 205 | 230 |
| 300 | 240 | 285 | 320 | 195 | 230 | 260 |
| 350 | 260 | 310 | 350 | 210 | 250 | 280 |
| 400 | 280 | 335 | 380 | 225 | 270 | 305 |
| 500 | 320 | 380 | 430 | 260 | 310 | 350 |
| 600 | 350 | 420 | 475 | 285 | 340 | 385 |
| 700 | 385 | 460 | 520 | 315 | 375 | 425 |
| 750 | 400 | 475 | 535 | 320 | 385 | 435 |
| 800 | 410 | 490 | 555 | 330 | 395 | 445 |
| 1000 | 455 | 545 | 615 | 375 | 445 | 500 |
Values per NEC 2023 Table 310.16. Small-conductor rule, 240.4(D): overcurrent protection may not exceed 15 A for 14 AWG copper, 20 A for 12 AWG copper (15 A for 12 AWG aluminum), 30 A for 10 AWG copper (25 A for 10 AWG aluminum), regardless of the ampacity in the table.
Which column to use: the termination rule
NEC 110.14(C): the ampacity used may not exceed the lowest temperature rating of any connected termination, conductor or device. Circuits rated 100 A or less, or conductors 14 through 1 AWG, are evaluated at 60 C unless the terminals are marked 75 C; circuits over 100 A or conductors larger than 1 AWG are evaluated at 75 C. Modern breakers, panelboard lugs and UL 486 mechanical and compression lugs are marked 75 C (CU or AL9CU 75/90), so the 75 C column is the working ampacity. A 90 C conductor such as THHN is still limited to its 75 C ampacity at the terminal; the 90 C rating is used only as the value that adjustment and correction factors are applied to, per 110.14(C)(2), which is why a derated THHN can often land on a 75 C lug at a higher ampacity than a 75 C conductor could.
Ambient temperature correction, Table 310.15(B)(1)
| Ambient | 60 C conductor | 75 C conductor | 90 C conductor |
|---|---|---|---|
| 21 to 25 C (70 to 77 F) | 1.08 | 1.05 | 1.04 |
| 26 to 30 C (78 to 86 F) | 1.00 | 1.00 | 1.00 |
| 31 to 35 C (87 to 95 F) | 0.91 | 0.94 | 0.96 |
| 36 to 40 C (96 to 104 F) | 0.82 | 0.88 | 0.91 |
| 41 to 45 C (105 to 113 F) | 0.71 | 0.82 | 0.87 |
| 46 to 50 C (114 to 122 F) | 0.58 | 0.75 | 0.82 |
| 51 to 55 C (123 to 131 F) | 0.41 | 0.67 | 0.76 |
| 56 to 60 C (132 to 140 F) | — | 0.58 | 0.71 |
Rooftop raceways: 310.15(B)(2) adds 33 C (60 F) to the ambient for conduit within 7/8 in of a roof surface in direct sunlight, which is the reason 90 C conductors are standard for PV and rooftop HVAC feeds.
More than three current-carrying conductors, Table 310.15(C)(1)
| Current-carrying conductors | Adjustment factor |
|---|---|
| 4 to 6 | 0.80 |
| 7 to 9 | 0.70 |
| 10 to 20 | 0.50 |
| 21 to 30 | 0.45 |
| 31 to 40 | 0.40 |
| 41 and over | 0.35 |
Neutrals carrying only the unbalanced current of a 3-wire circuit do not count; neutrals of a 4-wire wye serving nonlinear loads do (310.15(E)). Equipment grounding conductors never count. Raceway nipples 24 in or shorter are exempt.
Worked example
Nine 10 AWG THHN current-carrying conductors in one EMT in a 40 C mechanical room, landing on 75 C breakers. Start at the 90 C column: 40 A. Ambient correction for 90 C at 40 C: 0.91, giving 36.4 A. Adjustment for 7 to 9 conductors: 0.70, giving 25.5 A. Termination check: 75 C ampacity of 10 AWG is 35 A, and 25.5 A is below it, so the circuit ampacity is 25.5 A. 240.4(D) caps the breaker at 30 A; the next standard size below 25.5 A per 240.4(B) is 25 A, or 30 A is permitted since 25.5 rounds up to the next standard size only when the conductor is not 14, 12 or 10 AWG; for 10 AWG the cap holds, so a 25 A breaker is the conservative choice and many engineers accept 30 A under 240.4(B). This is the calculation behind pulling 8 AWG for 30 A circuits in a full raceway.
Feeder and service quick reference, 75 C copper
| Service or feeder | Copper | Aluminum | Neutral (reduced per 220.61) | Note |
|---|---|---|---|---|
| 100 A | 3 AWG (4 AWG under 310.12) | 1 AWG (2 AWG under 310.12) | same or one size smaller | 310.12 allows 83 percent for dwelling services |
| 125 A | 1 AWG | 2/0 | ||
| 150 A | 1/0 | 3/0 | ||
| 200 A | 3/0 (2/0 under 310.12) | 250 kcmil (4/0 under 310.12) | 1/0 Cu or 2/0 Al typical | the residential standard |
| 225 A | 4/0 | 300 kcmil | ||
| 400 A | 500 kcmil or 2 x 3/0 | 750 kcmil or 2 x 250 | parallel sets need identical length and lugs | |
| 600 A | 2 x 350 kcmil | 2 x 500 kcmil | ||
| 800 A | 3 x 300 kcmil or 2 x 600 | 3 x 500 kcmil | ||
| 1200 A | 4 x 350 kcmil | 4 x 500 kcmil |
Quick answers
What is the ampacity of 4/0 copper? 230 A at 75 C, 260 A at 90 C, 195 A at 60 C, per Table 310.16. Terminations at 75 C make 230 A the working value.
Why use the 75 C column when THHN is rated 90 C? NEC 110.14(C) limits ampacity to the terminal rating, and lugs and breakers are 75 C. The 90 C value is only the starting point for correction and adjustment factors.
What size wire for a 200 A service? 3/0 copper or 250 kcmil aluminum at 75 C; 2/0 copper or 4/0 aluminum is permitted for a dwelling service under 310.12.
What is the ampacity of 2 AWG aluminum? 90 A at 75 C, 100 A at 90 C, 75 A at 60 C.
Conversions Tech lugs are marked 75 C and 90 C (AL9CU or CU9) so the 75 C column applies without penalty; see compression lugs, mechanical lugs and neutral bars. Related: conduit fill, torque chart, AWG to kcmil.
