Voltage Drop Calculator

Calculate voltage drop in electrical circuits based on wire size, current, and distance.

System Voltage (V)

Current (Amps)

Distance (one-way, ft)

Wire Size (AWG)

Conductor Material

Phase

Voltage Drop (V)

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Voltage Drop (%)

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Voltage at Load

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Recommended Wire Size

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How It Works

Voltage drop is calculated using the formula Vd = 2 x K x L x I / Cm (single phase) or Vd = 1.732 x K x L x I / Cm (three phase). K is the resistivity constant (12.9 for copper, 21.2 for aluminum). NEC recommends voltage drop not exceed 3% for branch circuits.

About this Calculator

The Voltage Drop Calculator is a free, easy-to-use tool for electrical, wire, amps. Simply enter your values and get instant, accurate results — no signup, no ads, no tracking. All calculations run locally in your browser, so your data stays completely private.

Privacy Note: All calculations are performed locally in your browser. No data is ever sent to a server or third party.