Voltage Drop Calculator

Calculate wire voltage drop based on wire gauge (AWG), length, current, and material. NEC recommends keeping voltage drop below 3%.

Inputs

Voltage Drop
2.997 V
2.5% — ✓ Within NEC 3% limit

Results

PropertyValue
Wire gaugeAWG 10
Resistance (Copper)0.9989 Ω/1000ft
Round-trip resistance0.1998 Ω
Voltage drop2.997 V
% Voltage drop2.5%
End voltage117 V

Copper Wire Resistance (Ω/1000 ft)

AWGCopperAluminumArea (cmil)
4/00.049010.0805211,600
3/00.06180.1015167,800
2/00.077930.128133,100
1/00.098270.1615105,600
10.12390.203683,690
20.15630.256766,360
30.1970.323752,620
40.24850.408241,740
60.39510.649126,250
80.62821.03216,510
100.99891.64110,380
121.5882.6086,530
142.5254.1484,107
164.0166.5952,583
186.38510.491,624
2010.1516.681,022

Calculate voltage drop across a wire run with our free calculator, important for electrical installations to ensure devices receive adequate voltage.

How It Works

Voltage Drop = Current × Resistance, where wire resistance depends on wire gauge, length, and material (typically copper or aluminum). Longer wire runs and thinner gauges (higher resistance) produce greater voltage drop.

How to Use This Calculator

  1. Enter the current draw of your circuit
  2. Enter wire length (one-way distance)
  3. Select wire gauge and material
  4. Click Calculate to see voltage drop and percentage

Frequently Asked Questions

What's an acceptable voltage drop percentage?

Common electrical guidelines suggest keeping voltage drop under 3-5% for most circuits, though specific requirements vary by application and local electrical codes.

Why does wire gauge affect voltage drop?

Thinner wires (higher gauge number) have higher resistance per unit length, causing more voltage drop for the same current and distance compared to thicker wires.

Does wire length count one-way or round-trip?

Voltage drop calculations typically account for the complete circuit (out and back), so round-trip distance matters, check your specific calculator's convention.

What happens if voltage drop is too high?

Excessive voltage drop can cause devices to underperform, motors to run hot, or lights to dim, especially noticeable at the far end of long wire runs.