Wire Size vs Distance Chart: How Far Can You Run?
Maximum Wire Run Chart (3% Voltage Drop, Copper)
| Wire Size | 15A, 120V | 20A, 120V | 20A, 240V | 30A, 240V | 50A, 240V |
|---|---|---|---|---|---|
| 14 AWG | 45 ft | — | — | — | — |
| 12 AWG | 70 ft | 55 ft | 110 ft | — | — |
| 10 AWG | 115 ft | 85 ft | 170 ft | 115 ft | — |
| 8 AWG | 180 ft | 135 ft | 270 ft | 180 ft | 110 ft |
| 6 AWG | 290 ft | 215 ft | 430 ft | 285 ft | 170 ft |
| 4 AWG | 460 ft | 340 ft | 680 ft | 455 ft | 270 ft |
Values are for copper conductors at 75°C, full rated load. For aluminum, reduce distances by 25%. For partial loads, distances increase proportionally.
Tips for Long Wire Runs
- Use 240V instead of 120V: Same power at half the current → half the voltage drop → twice the distance
- Upsize the wire: Going from 12 AWG to 10 AWG increases max distance by 55%
- Use aluminum for large feeders: 2/0 aluminum costs 50% less than 1/0 copper and runs similar distances
- Consider a sub-panel: For outbuildings, run a 240V feeder to a sub-panel near the load rather than long branch circuits
Frequently Asked Questions
How far can I run 10 AWG wire?
For 20A at 120V: 10 AWG copper runs 95 ft before exceeding 3% voltage drop. For 20A at 240V: 190 ft. For 30A at 240V: 125 ft. These assume full rated load.
What happens if wire run is too long?
Excessive distance causes voltage drop. Equipment receives lower voltage, motors overheat, lights dim, electronics malfunction. The wire may be within ampacity limits but still cause problems due to voltage drop.
How do I calculate wire distance?
Rearrange the voltage drop formula: L_max = (VD% × V × 1000) ÷ (2 × I × R × 100). For single-phase. Where V = voltage, I = current, R = resistance/1000ft.
Disclaimer: For preliminary design only. Verify against local codes and professional engineering requirements.