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Wire Size & Voltage Drop Calculator

Find a planning-level cable size from voltage, load, distance and your voltage-drop target for DC, single-phase AC and three-phase circuits.

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Designed around the real sizing problemEnter watts or amps, use the actual one-way cable distance, choose copper or aluminum, and get the next standard metric size plus an approximate AWG equivalent. The calculation is transparent so you can see why the recommendation changes.

Size Your Cable

1. Circuit type
2. Load
Use the nominal source voltage. For solar PV, use the actual string/system voltage used for the run.
Enter the design current for the cable run.
3. Cable run
Enter the physical one-way distance. The calculator applies the circuit path factor automatically.
This is a planning target, not a universal code limit. The appropriate limit depends on the installation and jurisdiction.
Voltage-drop sizing is only one part of cable selection. Final installations also require checks for ampacity, insulation temperature, installation method, protection, short-circuit withstand and the electrical code that applies to the project.

What the Calculator Does

It converts your load into current when needed, calculates conductor resistance from material and cross-sectional area, applies the correct circuit path factor, and selects the smallest standard metric size that meets your chosen voltage-drop target.

Useful for Solar & Inverters

DC mode is suited to planning runs such as solar-array wiring, battery-to-inverter cables and other low-voltage DC loads. One-way length is doubled internally for the outgoing and return conductors.

Formula

Vdrop = I × R × path factor

The path factor is 2 for DC and single-phase circuits and √3 for balanced three-phase calculations.

Frequently Asked Questions

Yes. Enter one-way physical distance. DC and single-phase calculations use a 2× path factor for the outgoing and return conductors. Balanced three-phase uses √3 × one-way length in the voltage-drop calculation.
Yes. For DC and single-phase AC the calculator derives current from watts and voltage, with power factor applied when relevant. For three-phase AC, it uses the three-phase power relationship and the selected power factor.
No. Voltage drop is only one design check. Ampacity, insulation rating, installation method, ambient temperature, grouping, protection and local electrical requirements must also be checked before an installation is finalized.
For the same power, lower voltage requires more current. Higher current creates more voltage drop and resistive loss, so a low-voltage 12V, 24V or 48V run can need substantially more conductor area than a higher-voltage circuit of the same power.
No. AWG and metric cross-sectional sizes are different standards. The calculator shows an approximate AWG equivalent for the selected metric size; use the actual cable datasheet and applicable standard when purchasing or specifying cable.
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