Voltage Drop Calculator
Calculate voltage drop, end voltage, and wire resistance for single and three phase circuits.
What is the Voltage Drop Calculator?
The Voltage Drop Calculator is a free online tool for electricians and engineers to estimate voltage loss in a circuit based on wire gauge, material, length, current, and phase type. It checks results against NEC recommendations to help ensure safe and efficient electrical installations.
How to Use
- Enter the source voltage and circuit current in amperes.
- Input the one-way wire length and select feet or meters.
- Choose the wire gauge (AWG), phase type, and conductor material.
- Click Calculate Voltage Drop to see drop, end voltage, resistance, and NEC compliance.
Frequently Asked Questions
What is the NEC voltage drop limit?
The National Electrical Code recommends a maximum voltage drop of 3% for branch circuits and 5% for feeders to ensure efficient operation and safety.
Why does aluminum have higher resistance?
Aluminum has a higher resistivity than copper, so its resistance per 1000 feet is approximately 1.6 times that of copper for the same gauge.
Should I use single-phase or three-phase?
Use single-phase for standard residential branch circuits. Use three-phase for industrial and commercial systems where higher power loads are common.
Is my data saved or shared?
No. All calculations run locally in your browser. BestCalc does not collect, store, or transmit any data.