350 kcmil Wire Ampacity & Specifications
350 kcmil copper wire carries 310A at 75°C (NEC Table 310.16), or 250A for aluminum, and is typically protected by a 300A breaker.
Calculations are built on the 2023 National Electrical Code (NEC) and cross-checked against the published code tables. How we verify. Last updated June 2026.
350 kcmil wire has an ampacity of 310A at 75°C for copper and 250A for aluminum (NEC Table 310.16). Its 60°C and 90°C copper ratings are 260A and 350A. It is commonly protected by a 300A breaker.
Copper 75°C
310A
Copper 90°C
350A
Aluminum 75°C
250A
Typical breaker
300A
350 kcmil Wire Specifications
| Ampacity — Copper (60 / 75 / 90°C) | 260 / 310 / 350 A |
| Ampacity — Aluminum (60 / 75 / 90°C) | 210 / 250 / 280 A |
| Cross-section | 350,000 circular mils |
| DC resistance — Copper | 0.0367 Ω / 1000 ft |
| DC resistance — Aluminum | 0.0605 Ω / 1000 ft |
| Typical voltage drop (240V) | 0.5% at 50 ft · 0.9% at 100 ft (at 300A) |
Common Uses for 350 kcmil Wire
- 310A copper feeders
- 350A service conductors
Ampacities are from NEC Table 310.16. 14, 12 and 10 AWG are limited to 15A, 20A and 30A overcurrent protection (240.4(D)). Terminations rated 60°C or 75°C usually cap the usable ampacity below the 90°C value.
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