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Single-Phase Voltage Drop Calculator

Calculate single-phase voltage drop from current, conductor resistance, and one-way length (VD = 2 × I × R × L ÷ 1000).

Formula

VD = (2 × I × R × L) ÷ 1000

VD
Voltage drop, in volts
I
Current, in amps
R
Conductor resistance, in ohms per 1000 ft
L
One-way circuit length, in feet

What this calculator does

Calculates voltage drop for a single-phase circuit, accounting for the round-trip conductor length.

Use cases

  • Size a single-phase branch circuit run for acceptable voltage drop
  • Check a residential or light-commercial circuit's expected voltage drop
  • Compare voltage drop at different one-way run lengths

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