kabelquerschnitt-berechnen.de

Cable • Resistance • Material

Calculate Conductor Resistance

Calculate the electrical resistance of a cable based on length, cross-section and conductivity.

Calculation Values

copper 58, aluminum 37

Note: This calculator provides a technical estimate for guidance only. For electrical installations, standards, protective measures, installation method, ambient temperature, grouping, protective devices and manufacturer specifications must also be checked.

Formula Used

R = L / (κ × A)

R is the conductor resistance in ohms, L the one-way cable length, κ the conductivity and A the cross-section.

Frequently Asked Questions

Why does resistance increase with length?

The longer the conductor, the greater its electrical resistance.

Why does resistance decrease with a larger cross-section?

A larger conductor cross-section provides more conductive area for the current and reduces resistance.

Is the value independent of temperature?

No. Resistance changes with temperature. This calculator provides a rough estimate.

Practical guidance

Calculate resistance of one conductor run

The calculator gives DC resistance from one-way length, cross-section and conductivity. A complete circuit may contain two or more conductor runs.

Input values explained

Cable length
Enter the one-way distance from supply point to load. The required return path is already represented by the selected formula.
Conductor cross-section
Enter the cross-section of one loaded conductor in mm², not the sum of all cores in a cable.
Conductivity κ
κ is the calculation value for the conductor material. Common approximations are 58 for copper and 37 for aluminium; heating increases actual resistance.

Example: 25 m of 2.5 mm² copper

Use κ = 58 for one 25 m copper conductor of 2.5 mm².

R = 25 m ÷ (58 × 2.5 mm²) ≈ 0.1724 Ω

Line and return together would be about 0.3448 Ω under the same assumptions. The calculator displays one run only.

Temperature raises resistance

A warm conductor has more resistance than the constant-conductivity approximation used here.

Calculation limits

  • Terminals and contact resistance are excluded.
  • Large conductors and higher AC frequencies may introduce additional effects.