Voltage Drop Calculator

Formula and units

DC: ΔV = 2 × I × L × R. AC: ΔV = K × I × L × (R × PF + X × √(1 − PF²)), where K = 2 single phase or √3 balanced three phase.

How to use these results

Length is ONE WAY, not out-and-back. R and X are per conductor from manufacturer data at the relevant temperature and frequency; L is normalized to the same km or 1,000 ft basis. AC uses lagging displacement power factor and a steady-load approximation. Three-phase voltage is line-to-line. DC ignores X and PF. This is not an AWG selector, ampacity check or code compliance determination.

Verify critical electrical work with a qualified professional and applicable manufacturer instructions.

Worked example

DC 24 V, 10 A, 30 m one-way and R = 1 Ω/km gives 0.6 V drop (2.5%) and 23.4 V receiving voltage. Single-phase 230 V with X = 0.5 Ω/km and PF = 0.8 gives 0.66 V.

Reference

Formula background: Schneider Electric — Voltage drop in steady load conditions. The assumptions and input validation above define this calculator’s scope.