What this calculator does

It works out the voltage drop, the % drop, the voltage at the load and the power lost in the cable. Enter the phase, voltage, load (kW or A), power factor, conductor material, cable size, insulation and one-way length. It also checks the result against your maximum allowed drop.

How it is calculated

Resistance ρ_T = ρ₂₀ [1 + α (T − 20)] Cu ρ₂₀ = 0.01724, Al 0.0282 Ω·mm²/m; PVC 70 °C, XLPE 90 °C Single phase VD = 2 · I · R · PF Three phase VD = √3 · I · R · PF (line-to-line voltage, balanced load) Power loss 2 · I² · R (1-ph) or 3 · I² · R (3-ph)

Conductor temperatures follow IEC 60364-5-52 / BS 7671. Reactance is not included; it becomes significant from about 50 mm².

Questions

What is an acceptable voltage drop?

Many projects use limits of about 3–5 %, but the allowed value depends on the code and the authority on your project. Enter the project limit in "Maximum voltage drop".

Is the length one-way?

Yes. Enter the one-way route length. The formula already counts the return path.

Related

Breaker & Cable Sizing · Electrical Load & MDB · Generator Set Sizing

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Results are for preliminary design. Verify final selections against project specifications, applicable codes and manufacturer data.