Voltage Drop & Wire Gauge Calculator
Calculate circuit voltage loss over distance and automatically select recommended copper conductor gauge.
Electrical Circuit Parameters
Frequently Asked Questions
What is the acceptable voltage drop according to the NEC?
The National Electrical Code (NEC Article 210.19) recommends that maximum voltage drop for branch circuits should not exceed 3% for optimal electrical efficiency, and total combined feeder plus branch circuit voltage drop should not exceed 5%.
Why does voltage drop increase over long distances?
Every conductor has internal electrical resistance. As distance increases, the total resistance increases proportionally. By Ohm’s Law (V = I × R), higher resistance causes a larger voltage drop across the wire before power reaches the device.
How do you fix excessive voltage drop?
To reduce voltage drop on long wire runs (e.g., running power 100+ feet to a detached shed or sub-panel), increase the wire size to a thicker gauge (e.g., upsizing from 12 AWG to 10 AWG or 8 AWG copper wire).