Voltage drop

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

Material	Conductance
Copper	56.0
Silver	62.5
Aluminium	35.0

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

*) 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 %	\(\displaystyle Δu=\frac{ΔU}{Un} ·100 \% \)