Voltage Drop Calculator
Calculate voltage drop in wire based on distance and load
Long wire runs cause voltage to drop due to resistance. This calculator helps you determine if your wire size is sufficient for the distance and load.
Calculator Inputs
Circular Mils
Results
Enter values above to see your results
How It Works
Formula: VD = (2 × K × I × L) / CM. (For 3-phase, substitute 2 with √3).
Tips & Best Practices
- •NEC recommends a maximum voltage drop of 3% for branch circuits and 5% for feeders.
- •Upsizing wire reduces voltage drop and wasted energy.
Frequently Asked Questions
What is K factor?
It represents the resistivity of the material. Copper is ~12.9, Aluminum is ~21.2.
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