Voltage drop calculator

Two-wire DC or resistive single-phase loop: voltage drop = 2 × length × current × resistivity ÷ conductor area.

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One-way wire length (meters)

Current (amps)

More inputs and assumptions

Conductor area (mm²)

Resistivity at operating temperature (Ω·mm²/m)

Supply voltage (volts)

Answer

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Two-wire DC or resistive single-phase loop: voltage drop = 2 × length × current × resistivity ÷ conductor area.

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Precision and calculation record

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Formula and assumptions

Uses resistivity you supply at the operating temperature. The resistivity default is an illustrative input, not a material specification or installation approval. Contact resistance, reactance, three-phase circuits, temperature rise and code limits are excluded. Enter a permitted voltage-drop limit separately when sizing a conductor.

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Updated 2026-09-29

Using Voltage drop calculator

Two-wire DC or resistive single-phase loop: voltage drop = 2 × length × current × resistivity ÷ conductor area.

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A worked example

For one-way wire length (meters) = 20, current (amps) = 10, conductor area (mm²) = 2.5, resistivity at operating temperature (ω·mm²/m) = 0.017241, supply voltage (volts) = 230, voltage drop (volts) = 2.75856.

Before you use the result

Example results for one-way wire length (meters)

These examples use Current (amps): 10; Conductor area (mm²): 2.5; Resistivity at operating temperature (Ω·mm²/m): 0.017241; Supply voltage (volts): 230. They are reference calculations, not recommended settings.

One-way wire length (meters)	Voltage drop (volts)
10	1.37928
20	2.75856
40	5.51712

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