Calculate wire resistance

Online calculators and formulas for calculating wire resistance

Calculate wire resistance online

On this page the electrical resistance, the length or the Cross-sectional area of a wire can be calculated. Two of the three values and the resistivity or conductivity of the material of the wire must be known.

The specific conductance values of the most common cables are



Copper 56.0
Silver 62.5
Aluminium 35.0

For a list of other resistivity and conductance values click here.

Online calculator

Enter the following values:
Length of wire [ m ]
Cross-sectional area [ mm2 ]
Enter one of the two following values:
Specific resistance [ Ω ]
or conductance [ S ]
Wire resistance
Wire conductance
Decimal places

Wire resistance formulas

Calculate wire resistance

if the length and cross-section are known

\(\displaystyle R=\frac{ρ · l}{A}\)
\(\displaystyle R=\frac{l}{σ · A}\)

Calculate the length of the wire

if the resistance and cross section area are known

\(\displaystyle l=\frac{R · A}{ρ}\)
\(\displaystyle l=R · A · σ \)

Calculate the wire cross-section

when resistance and length are known

\(\displaystyle A=\frac{l}{R · σ}\)
\(\displaystyle A=\frac{l · ρ}{R}\)


\(\displaystyle A \) Cross-section area

 \(\displaystyle l \)  Length

\(\displaystyle R \) Resistance of the wire

\(\displaystyle S \) Conductivity of the wire

\(\displaystyle ρ \) Specific resistance

\(\displaystyle σ \) Specific conductance