Voltage Drop Calculator - Wire Size, NEC 3% & 5% (Free)
Every metre of wire quietly steals a little voltage. As current pushes through a conductor's resistance, some voltage is lost as heat before it ever reaches the load — that's voltage drop . Too much of it and lights dim, motors overheat, and sensitive electronics misbehave. This free Voltage Drop Calculator tells you exactly how much voltage you'll lose for a given current, wire size, length and material — for single-phase, three-phase or DC — and checks it against the NEC 3% and 5% recommendations so you know whether to upsize your conductor. Table of Contents The Voltage Drop Calculator What Is Voltage Drop? The Voltage Drop Formula NEC 3% & 5% Limits Single-Phase vs Three-Phase Copper vs Aluminium How to Reduce Voltage Drop Worked Examples Common Mistakes FAQ The Voltage Drop Calculator Choose imperial (AWG) or metric (mm²), enter the circuit details, and get the voltage drop in volts and pe...