Conductors and wiring

Copper and aluminium conductor resistance calculator

Estimate DC resistance from conductor material, nominal area, path length and operating temperature, with optional voltage-drop and I²R loss context.

Calculate

Conductor path
mm²
m
°C
Optional load contextOptional
A
Adds simple IR voltage drop and I²R loss only.

Worked example

Resistance at operating temperature

 Ω

Resistance at 20 °C
 Ω
Conductor path length included
200 m

Annealed copper; DC resistance from nominal area. AC skin and proximity effects are excluded, and the optional IR value is a resistive series component rather than necessarily the change in AC terminal voltage.

Underlined figures are rounded. Select one to copy its full value.

Method and assumptions

Formula

R20 = ρ20 × length ÷ area; RT = R20 × (K + T) ÷ (K + 20)

Uses annealed copper at 100% IACS and aluminium at 61% conductivity. K is 234 for copper and 228 for aluminium.

Limits of this result

  • Actual conductor resistance varies with material grade, stranding, compaction, joints and manufacturing tolerance.
  • This uses DC resistance. AC skin, proximity and frequency-dependent losses are excluded.
  • Optional IR is the resistive series-voltage component, not necessarily the change in AC terminal-voltage magnitude; it is not an ampacity, protection or code-compliant cable selection.

Technical sources

  1. Power Cable Installation Guide — resistance at other temperaturesSouthwire · Chapter 2, accessed 2026-09-14
  2. Physical properties of fully dense copperCopper Development Association · Standards Handbook data; accessed 2026-09-14

Put the value to work

Read the related engineering guidance, or carry this task into System Builder to identify the signal path and EpiSensor products.

Continue in System Builder Read: Selecting Current Transformers

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