# Voltage Drop Calculator

> Voltage drop calculator: find wire voltage drop and end of run voltage from length, current, wire gauge, and material, AC or DC. Free, private, runs locally.

- **Canonical URL:** https://boringtoolskit.com/voltage-drop-calculator/
- **Category:** Everyday Calculators
- **Evidence level:** authored-methodology
- **Reviewed:** August 2026
- **Last verified:** 2026-10-12
- **Privacy:** Inputs and results stay in this browser unless the page clearly labels an external request.

## How it works

Voltage drop = 2 x length (ft) x amps x resistance per 1,000 ft / 1,000 (round-trip run); drop % = drop / volts x 100.

## Worked example

120 V circuit, 15 A, 100 ft of AWG 0 wire: 4.76 V dropped across the round trip, a 3.97% drop, under the 5% rule of thumb.

## Sources

- [Calculation methodology and verification standard](/methodology/)

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