Conductors and wiring

Voltage drop calculator

Estimate steady-state voltage drop or rise from circuit arrangement, one-way route length and manufacturer resistance/reactance values.

Calculate

Circuit and route
V
A
m
Conductor impedance

Use manufacturer values for the installed conductor and operating temperature.

Ω/km
Ω/km

Worked example

Voltage drop, line-to-line

 V

Change as a share of nominal voltage (signed)
 %
Receiving-end voltage, line-to-line, estimated
 V
Series-impedance voltage magnitude
 V
Resistive component
 V
Reactive component (signed)
 V

Balanced three-phase first-order estimate. This is not an ampacity, protection or code-compliance result.

Underlined figures are rounded. Select one to copy its full value.

Method and assumptions

Formula

1φ: ΔU = 2IL(R cosφ ± X sinφ); balanced 3φ: ΔU = √3IL(R cosφ ± X sinφ); DC: ΔU = 2ILR

Length L is one-way in kilometres; R and X are per-conductor Ω/km. Add X for lagging loads and subtract it for leading loads.

Limits of this result

  • Use resistance and reactance from the actual cable or busway manufacturer at the applicable operating conditions.
  • The AC result is a first-order longitudinal voltage-change approximation, intended only where total series-impedance voltage is no more than 10% of nominal circuit voltage. Outside that domain the receiving-end estimate is suppressed.
  • The balanced three-phase shortcut does not model neutral current, harmonics, unbalance, starting transients or distributed loads.
  • This result is not an ampacity, protection, fault-duty or jurisdictional cable-selection check.

Technical sources

  1. Calculation of voltage drop in steady load conditionsSchneider Electric Electrical Installation Guide · accessed 2026-09-14
  2. Voltage Drop Calculator scope and professional-use constraintsSouthwire · accessed 2026-09-14

Put the value to work

Read the related engineering guidance, or carry this task into System Builder to identify the signal path and EpiSensor products.

On this page