Voltage drop

Online calculators and formulas for calculating the voltage loss in a wire

Calculate loss voltage of a wire

This page calculates the voltage drop that is lost in a wire due to its resistance. To do this, the input voltage, the current, the simple cable length and the cable cross-section must be specified.

A phase shift in the case of inductive loading can be specified as an option. A value of 1 is preset for Cos φ for ohmic load and direct current.

The specific resistance or the conductance can be specified for the material of the conductor. The following table contains the most common values of the conductance.

The specific conductance values of the most common cables are



Copper 56.0
Silver 62.5
Aluminium 35.0

For a list of other specific resistances and conductance values click here.

Voltage drop calculator

Voltage (V)
Load current (A)
Wire length (one way) (m) *)
Cross-sectional area (mm2)
Cos φ
Decimal places
Loss voltage
Useful voltage
Voltage drop
Wire resistance


\(\displaystyle A \) cross-section

 \(\displaystyle l \)  length

\(\displaystyle R \) Resistance of the wire

\(\displaystyle ρ \) Specific resistance

\(\displaystyle σ \)Specific conductance

\(\displaystyle Un \) Nominal voltage (input)

\(\displaystyle ΔU \) Loss voltage

*) Double the line length is calculated (outward and return line).

Formulas for voltage drop calculation

Single wire resistance \(\displaystyle R=\frac{ρ · l}{A}\) \(\displaystyle =\frac{l}{σ · A}\)
Total wire resistance \(\displaystyle R=2 ·\frac{ρ · l}{A}\) \(\displaystyle =2 ·\frac{l}{σ · A}\)
loss voltage \(\displaystyle ΔU=2 ·\frac{l}{σ · A}· I · cos( φ) \)
voltage drop in % \(\displaystyle Δu=\frac{ΔU}{Un} ·100 \% \)

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