Voltage Drop Calculator
Voltage loss over wire length
Voltage drop
—
📚 Learn more — how it works, FAQ & guide Click to expand
Learn more — how it works, FAQ & guide
Click to expand
Voltage drop calculator
Calculate voltage loss across a wire run. Meet NEC 3% recommendation.
How to use this tool
- 1
Enter current (amps)
Load current the circuit carries.
- 2
Enter wire length
One-way distance from source to load.
- 3
Pick AWG + material
See voltage drop + percentage.
Frequently Asked Questions
What is acceptable voltage drop?
NEC recommends max 3% for branch circuits, 2% for feeders. Combined total should not exceed 5%.
Single vs three phase formula
Single phase: Vdrop = 2 × I × R × L. Three phase: Vdrop = √3 × I × R × L. Three-phase has lower drop for same load.
You might also like
🔒
100% Privacy. This tool runs entirely in your browser. Your data is never uploaded to any server.