3 AWG voltage drop at 100 feet
Computed voltage drop for 3 AWG copper conductors on a 100 ft one-way run.
3.92 V
drop on 3 AWG copper, 100 ft one-way, 80 A load · 3.3% of 120 V · 1.6% of 240 V
3 AWG at 100 ft by load
| Load | Drop | % at 120 V | % at 240 V | 3% rule (240 V) |
|---|---|---|---|---|
| 20 A | 0.98 V | 0.8% | 0.4% | OK |
| 40 A | 1.96 V | 1.6% | 0.8% | OK |
| 60 A | 2.94 V | 2.5% | 1.2% | OK |
| 80 A | 3.92 V | 3.3% | 1.6% | OK |
Vd = 2 × length × R × I ÷ 1000, R = 0.245 Ω/1000 ft (copper, NEC Ch. 9 Table 8). Aluminum is about 1.6× higher.
Same wire, other distances
25 ft · 50 ft · 75 ft · 125 ft · 150 ft · 200 ft · 250 ft · 300 ft
FAQ
What is the voltage drop on 3 AWG wire at 100 feet?
At 80 A (80% of its 100 A 75°C rating) 3 AWG copper drops 3.92 V over 100 ft one-way: 3.3% at 120 V or 1.6% at 240 V.
How far can I run 3 AWG at 80 amps?
To stay within 3% at 120 V, about 92 ft one-way; at 240 V about 184 ft.