Electric Circuits Voltage Drop

Calculate voltage drop in electric circuits using Ohm's law and other methods. Voltage drop is calculated using resistance and current, or by using specific resistivity with wire properties, or by using conductor factors.

Voltage Drop Calculator

Voltage drop in an electric circuit can be calculated using Ohm's law:

U = R × I

where:

  • U = voltage drop (volts, V)
  • R = electrical resistance (ohms, Ω)
  • I = current (amps, A)

Alternatively, using wire properties:

U = K × P × L × I / A

where:

  • K = specific resistivity (Ω - circular mils/foot)
  • P = phase constant (2 for single phase, 1.732 for three phase)
  • L = wire length (ft)
  • A = wire area (circular mils)

Or using conductor factor:

U = f × I × L

where:

  • f = factor from lookup table
  • I = current (amps)
  • L = conductor length (ft)
Calculator

Inputs

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Voltage Drop (U)-- V
Calculator

Inputs

Results

Voltage Drop (U)-- V
Calculator

Inputs

Results

Voltage Drop (U)-- V
AWGMetric (mm²)Single-Phase FactorThree-Phase Factor
142.080.4760.42
123.310.3130.26
105.260.1960.17
88.370.1250.11
613.30.08330.071
421.20.05380.046
3-0.04310.038
233.60.03230.028
142.40.03230.028
1/053.50.02690.023
2/067.40.02220.02
3/0850.0190.016
4/0107.20.01610.014
250-0.01470.013
300-0.01310.011
350-0.01210.011
400-0.01150.009
500-0.01010.009