Electrical
Conductor Ampacity Table
Allowable ampacity for copper and aluminum conductors at the 60, 75, and 90 degree C columns, for not more than three current-carrying conductors at 30 degrees C ambient.
Source of these values
Values as commonly published for NFPA 70 (National Electrical Code) Table 310.16. Reproduced for convenience. Verify against the edition adopted in your jurisdiction.
| Size | Cu 60 C | Cu 75 C | Cu 90 C | Al 60 C | Al 75 C | Al 90 C |
|---|---|---|---|---|---|---|
| 14 | 15 | 20 | 25 | — | — | — |
| 12 | 20 | 25 | 30 | 15 | 20 | 25 |
| 10 | 30 | 35 | 40 | 25 | 30 | 35 |
| 8 | 40 | 50 | 55 | 35 | 40 | 45 |
| 6 | 55 | 65 | 75 | 40 | 50 | 55 |
| 4 | 70 | 85 | 95 | 55 | 65 | 75 |
| 3 | 85 | 100 | 115 | 65 | 75 | 85 |
| 2 | 95 | 115 | 130 | 75 | 90 | 100 |
| 1 | 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 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 |
In short
Allowable conductor ampacity depends on size, material, and insulation temperature rating. At the 75 degree C column, copper carries 25 amperes at 12 AWG, 35 at 10 AWG, 50 at 8 AWG, and 65 at 6 AWG. These figures assume not more than three current-carrying conductors in a raceway at a 30 degree C ambient, and correction and adjustment factors apply on top of them.
Notes and limits
- Based on not more than three current-carrying conductors in a raceway, cable, or earth, at an ambient of 30 degrees C.
- The ambient correction factor and the adjustment factor for more than three current-carrying conductors both apply on top of these figures.
- The 90 degree C column is normally used only as a starting point for derating. Per 110.14(C), the finished ampacity cannot exceed the column matching the lowest-rated termination, which is commonly 60 or 75 degrees C.
- 240.4(D) separately limits the overcurrent device for small conductors: 15 A for 14 AWG copper, 20 A for 12 AWG copper, and 30 A for 10 AWG copper, with limited exceptions.
- This is the table for the general case. Other installation methods, such as conductors in free air, use different tables.
Direct contact
Have a controls question?
Reach Eric Sullivan directly about anything on this site, a controls or automation topic, or one of his personal projects.