⚡ Voltage Drop Calculator
Calculate voltage drop across a wire run based on material, gauge, distance, and current load.
Circuit Details
Your Result
Formula: Voltage Drop = (Phase Factor × K × Distance × Current) / Circular Mils, where K is the resistivity constant for the wire material.
How the Voltage Drop Calculator Works
Voltage drop occurs because every wire has resistance. Longer runs, higher current, and thinner (smaller AWG number = larger, higher AWG number = smaller) wire all increase voltage drop. The National Electrical Code (NEC) recommends keeping voltage drop under 3% for branch circuits and 5% total from source to the farthest outlet.
Formula
Percent Drop = Voltage Drop / System Voltage × 100
K (Copper) = 10.371 Ω·cmil/ft, K (Aluminum) = 16.864 Ω·cmil/ft
Phase Factor: Single-Phase = 2, Three-Phase = 1.732 (√3)
Frequently Asked Questions
What is an acceptable voltage drop?
The NEC recommends no more than 3% voltage drop on a branch circuit and no more than 5% total (feeder + branch) for optimal equipment performance.
How do I reduce voltage drop?
Use a larger wire gauge (lower AWG number), shorten the wire run, or reduce the current draw on the circuit.