Calculatium

Resistive Voltage Drop Calculator

Estimate resistive voltage drop from cable length, current, cross-section and resistivity. An approximate calculation, not a cable-sizing certificate.

Enter your values

The starting values are editable examples. Results update when you change your inputs.

Example: 10
Example: 5
Example: 2.5
Example: 0.0175
Example: 12

Your result

Updates as you change your values.

Enter values to calculate.

How it is calculated

DC round trip: ΔV ≈ 2ρLI/S. Balanced resistive three-phase: ΔV ≈ √3ρLI/S. Drop percentage = ΔV / nominal voltage × 100.

Worked example

For a 12 V DC circuit with 10 m one-way length, 5 A, 2.5 mm² conductors and resistivity 0.0175 Ω·mm²/m, drop is 0.7 V, or about 5.83%.

Before you calculate

Enter one-way cable length; the DC formula already includes the outward and return paths. Use consistent length and area units and a resistivity appropriate to the material and assumptions. Select the circuit model that matches the simplified calculation.

Interpreting the result

The model excludes reactance, power factor in the drop equation, heating and real installation conditions. It does not select a compliant conductor or protection device. Actual wiring design requires technical review and applicable regulations.

Use the units shown beside each field. Monetary fields labelled EUR stay in euros; changing language does not exchange currencies. Results are estimates under the stated assumptions.