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Free Voltage Drop Calculator
Calculate the voltage drop for any wire run based on wire material (copper or aluminum), wire gauge (AWG), run length, load current, and source voltage. Results include voltage drop, percentage drop, and voltage at the load, with NEC 3% and 5% guideline indicators.
Frequently asked questions
What is the NEC voltage drop recommendation?
The NEC recommends a maximum 3% voltage drop for branch circuits and 5% total (feeder + branch). Excessive voltage drop causes equipment to run hot, reduces efficiency, and can damage motors.
What wire gauge should I use for a long run?
For runs over 50 feet, consider upsizing the wire one gauge. For runs over 100 feet, upsize two gauges. Use this calculator to verify your voltage drop is within NEC guidelines.
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