Electrical Calculators

Voltage Drop Calculator

Estimate voltage drop using US AWG/feet or IEC-style metric mm²/metres inputs.

Reviewed July 26, 2026 Runs locally No sign-up

United States / AWGPreliminary engineering estimate

=Your result will appear here

Enter values and calculate.

APPLICABILITY

Where this result fits

Region: United States / AWG · IEC / UK–EU metric · Code limits are regional
Result type: Preliminary engineering estimate
Standards basis: NFPA 70 — National Electrical Code; IEC 60364-5-52:2009 + AMD1:2024 — Wiring systems
Edition / version: IEC 60364-5-52:2009 + AMD1:2024; BS 7671:2018+A3:2024 / A4:2026 transition; NFPA 70 (NEC) 2026 reference

Important: The calculated drop is an estimate. Conductor temperature, reactance, harmonics, connection losses, installation method, and local design limits may change the final requirement. Electrical safety policy

STEP BY STEP

How to use the Voltage Drop Calculator

Choose the US AWG or IEC/UK–EU metric input mode.
Enter current, system voltage, one-way length, conductor material, phase, and conductor size.
For metric input, enter an estimated conductor temperature used only for resistance correction.
Review voltage drop and load voltage, then verify the design limit and conductor selection under the adopted local code.

ACCURACY & LIMITS

What to know before using the result

Resistance values are approximate and change with conductor temperature.
The formula omits AC reactance, harmonics and installation-specific losses; verify allowable drop and conductor sizing against the applicable code.

HELP

Frequently asked questions

How accurate is the Voltage Drop Calculator?

The calculator uses the formula shown on this page and keeps full numeric precision internally before formatting the result. Resistance values are approximate and change with conductor temperature.

Does the Voltage Drop Calculator upload my input?

No. The calculation or processing runs locally in your browser. UtiliNest does not receive or store the values you enter.

Can I use the Voltage Drop Calculator on a phone?

Yes. The inputs, result controls, and explanatory content are designed for current mobile and desktop browsers.

Where does the Voltage Drop Calculator apply?

Applicability: United States / AWG, IEC / UK–EU metric, Code limits are regional. Result classification: Preliminary engineering estimate. The calculated drop is an estimate. Conductor temperature, reactance, harmonics, connection losses, installation method, and local design limits may change the final requirement.

SOURCES

Definitions and references

Reviewed against the references below on July 26, 2026. Links open the source publisher's website. Read the source policy

NFPA 70 — National Electrical Code IEC 60364-5-52:2009 + AMD1:2024 — Wiring systems IET — BS 7671 edition and amendment status NIST Guide to the SI