How Many Amps Can 500 kcmil Copper Wire Handle?
Verified against NEC 2023, checked against the 2026 edition · Last checked August 19, 2026
500 kcmil copper wire carries 320 A at 60°C, 380 A at 75°C and 430 A at 90°C · Table 310.16. Which column applies depends on the termination rating · 110.14(C).
Common landing spot: a 350 A breaker or feeder.
| Column · insulation examples | Ampacity | Basis |
|---|---|---|
| 60°C · TW, UF | 320 A | Table 310.16 |
| 75°C · THW, THWN, XHHW wet, USE | 380 A | Table 310.16 |
| 90°C · THHN, THWN-2, XHHW-2 | 430 A | Table 310.16 |
THHW and XHHW are 90°C only in dry and damp locations; wet locations put them in the 75°C column. XHHW-2 and THWN-2 hold 90°C wet or dry · Table 310.4(1).
| Current-carrying conductors | Percent of table ampacity |
|---|---|
| 4 to 6 | 80% |
| 7 to 9 | 70% |
| 10 to 20 | 50% |
| 21 to 30 | 45% |
| 31 to 40 | 40% |
| 41 and more | 35% |
Ambient above 86°F applies a further correction from the band table of 310.15(B)(1). The free wire size calculator applies both automatically.
Derate it in seconds, offline.
The JobVolt app applies ambient correction, conductor adjustment and termination limits to 500 kcmil copper with every step cited, then exports inspector-ready PDF submittals.
Common questions
- How many amps can 500 kcmil copper wire handle?
- 320 A at 60°C terminations, 380 A at 75°C and 430 A at 90°C, per NEC Table 310.16 with no more than three current-carrying conductors at 86°F ambient.
- What size breaker goes on 500 kcmil copper?
- 350 A is the largest standard rating at or under the 75°C ampacity of 380 A · 240.6(A). Because that ampacity is not a standard rating, the next size up is sometimes permitted by 240.4(B) when the load allows.
- Does conduit fill change the ampacity of 500 kcmil copper?
- Four or more current-carrying conductors in one raceway derate the table value · 310.15(C)(1). At 4 to 6 conductors, 500 kcmil copper starts from 80% of the 90°C cell: 344 A before any further correction. Heat above 86°F derates it further · 310.15(B)(1).