Voltage Drop Calculator

Calculate voltage drop with VD = (2 × K × I × L) ÷ CM for single-phase and VD = (√3 × K × I × L) ÷ CM for three-phase, where K is 12.9 for copper and 21.2 for aluminum. Percent drop = (VD ÷ Source Voltage) × 100.

Compare results against the NEC 210.19(A) Informational Note No. 4 and 215.2(A)(1) Informational Note No. 2 recommendations: 3% maximum on a branch circuit and 5% maximum combined feeder plus branch circuit. The app flags PASS, WARNING, or FAIL for each limit.

Find the smallest AWG or kcmil conductor that keeps voltage drop within your target percentage, using circular mil values from 14 AWG (4,110 CM) through 1,000 kcmil. Results are cross-checked against NEC 310.16 ampacity so the selected size never undersizes protection.

Reverse-solve the maximum one-way run length for a given conductor size, load, and allowable drop percentage. Essential for long runs to outbuildings, pumps, EV chargers, and remote panels where voltage drop — not ampacity — drives the wire size.

Switch between copper and aluminum conductors with the correct K constant applied automatically. The app also supports AC and DC systems and lets you enter a power factor for accurate AC voltage drop on reactive loads such as motors and transformers.

Generate PDF calculation sheets showing inputs, formulas, voltage drop in volts and percent, compliance status, recommended conductor size, and the applicable NEC references. Export to CSV for project documentation. All calculations run offline on-device.