Voltage Drop Calculator
How to calculate voltage drop
- Choose copper or aluminium and the wire size in AWG or mm².
- Choose DC or single-phase, or three-phase, and enter the voltage and current.
- Enter the one-way length of the cable to see the drop and the voltage at the load.
Frequently asked questions
How much voltage drop is acceptable?
A common guide is no more than 3% on a branch circuit and 5% in total from the supply to the load. Check your local wiring rules.
Why the one-way length?
The current goes out and back, so the calculator counts both conductors for you.
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