What Size Wire for 225 Amps at 150 Feet?
Voltage-drop-aware wire sizing for a 225-amp circuit running 150 ft (one-way) at 240V — because over distance, voltage drop, not ampacity, often sets the wire size.
Calculations are built on the 2023 National Electrical Code (NEC) and cross-checked against the published code tables. How we verify. Last reviewed June 2026.
Actual drop 1.7%. For ≤5% drop: 4/0 (1.7%).
Actual drop 2.0%. For ≤5% drop: 300 kcmil (2.0%).
At 150 ft, ampacity still governs: 4/0 AWG copper carries 225A and its drop (1.7%) is already within 3% — no upsizing needed.
Voltage Drop at 150 Feet
Voltage drop is calculated for a 240V single-phase circuit over a 150 ft one-way run (conductor length doubled for the return). Sizes meeting the ≤3% target are highlighted.
| Wire size | Copper drop | Aluminum drop | Within 3%? |
|---|---|---|---|
| 4/0 | 1.7% | 2.8% | |
| 250 kcmil | 1.4% | 2.4% | |
| 300 kcmil | 1.2% | 2.0% | |
| 350 kcmil | 1.0% | 1.7% | |
| 400 kcmil | 0.9% | 1.5% | |
| 500 kcmil | 0.7% | 1.2% |
Drop % uses NEC Chapter 9, Table 8 DC resistance — an accepted approximation for typical power-factor AC branch circuits. The wire must also meet ampacity; both checks are applied above.
Different distance or voltage?
Open the calculator pre-filled with 225A, 240V, 150 ft to adjust material, temperature and drop target.