Should length be one-way or round-trip?

Enter the one-way distance from source to load. The calculator applies the appropriate return-path or phase factor for the selected circuit type.

What voltage drop is acceptable?

Many design references use 3% for branch circuits and 5% overall as planning targets, but the exact requirement depends on the installation and local code.

Does a larger wire reduce voltage drop?

Yes. Larger conductors have lower resistance, so the same load current loses less voltage over the run.

Voltage Drop Calculator

Estimate voltage drop, percent drop, conductor loss and recommended wire size for DC, single-phase and three-phase circuits.

Circuit type

Voltage, V

Load current, A

One-way length, ft

Wire size mode

Wire size (AWG/kcmil)

Conductor material

Conductor temperature, C

Load power factor

Load type (estimate limit)

Quick presets

Voltage drop from wire resistance

US English search results expect current, one-way distance, conductor material and wire size or cross-sectional area, with a percent drop result for DC, single-phase AC or balanced three-phase AC.

V_{d r o p} = I R_{l oo p}

The loop resistance depends on phase type, conductor length, material and size.

% d r o p = \frac{V _{d r o p}}{V _{so u r ce}} \times 100

Percent drop compares the lost voltage with the source voltage.

Wire size caveat

Not an electrical-code approval

Voltage drop is only one design check. Ampacity, insulation, temperature, conduit fill, fault current, equipment instructions and local code still need qualified review.

Frequently Asked Questions

Sources and References

Calculations are based on the listed reference sources. Links open in a new tab.

Updated: June 2, 2026

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