Wire Resistance Calculator

Online calculator for calculating the electrical resistance of wires

Calculation

m
mm²
Ω
Result
Wire resistance:
Wire cross-section:
Wire length:
Wire conductance:

Good to know

What is wire resistance?

Wire resistance describes the electrical resistance of a conductor. It depends on the length, cross-section, and material of the wire.

Specific conductance values
Material Conductance (S)
Silver 62.5
Copper 56.0
Aluminum 35.0
Basic formula
\[R = \frac{\rho \times l}{A} = \frac{l}{\sigma \times A}\]
With specific resistance \(\rho\) or conductance \(\sigma\)
Important note

For two-wire cables (e.g. speaker cable), the calculated value must be multiplied by 2: Total resistance = Forward + Return conductor

Formulas for wire resistance

Wire resistance (also called conductor resistance or resistance of a conductor) can be calculated using the following formulas. The specific resistance or conductance of the wire material must be known.

Wire resistance

\[R = \frac{\rho \times l}{A}\]
\[R = \frac{l}{\sigma \times A}\]

Wire length

\[l = \frac{R \times A}{\rho}\]
\[l = R \times A \times \sigma\]

Wire cross-section

\[A = \frac{l}{R \times \sigma}\]
\[A = \frac{l \times \rho}{R}\]

Variable legend

  • \(R\): Wire resistance (Ω)
  • \(l\): Wire length (m)
  • \(A\): Wire cross-section (mm²)
  • \(\rho\): Specific resistance (Ω⋅mm²/m)
  • \(\sigma\): Specific conductance (S⋅m/mm²)
  • \(S\): Wire conductance (S)

Practical notes

Two-wire cables

For two-wire cables (e.g. speaker cables), the calculated value must be multiplied by 2, since the current flows through both the forward and return conductor.

\[R_{\text{total}} = 2 \times R_{\text{single}}\]
Copper purity

The conductance of copper can vary depending on purity. The preset value of 56 corresponds to standard commercial cables.

→ More specific values

Extended material table
Material Specific resistance \(\rho\) (Ω⋅mm²/m) Specific conductance \(\sigma\) (S⋅m/mm²) Application
Silver 0.016 62.5 High frequency technology
Copper 0.0178 56.0 House installation, electrical
Aluminum 0.0286 35.0 High voltage lines
Gold 0.024 41.7 Contacts, electronics
Typical cross-sections
House installation:
Lighting: 1.5 mm²
Outlets: 2.5 mm²
Stove: 4-6 mm²
Main supply: 10-16 mm²
Automotive/Audio:
Car cables: 0.5-2.5 mm²
Speaker cables: 1.5-4 mm²
Starter cables: 25-50 mm²
Welding cables: 35-95 mm²


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