Voltage Drop Calculator
Estimate the voltage drop along a cable run.
Result
Results are estimates for general information only and are not professional advice.
Voltage drop
As current flows through a cable, some voltage is lost to the cable's resistance. The drop is 2 × length × resistance × current (the factor of 2 accounts for the return path). This calculator gives the drop in volts and as a percentage of the source.
Frequently Asked Questions
What is the Voltage Drop Calculator?
Estimate the voltage drop along a cable run. It runs instantly in your browser and is completely free to use.
What do I need to enter to use the Voltage Drop Calculator?
The Voltage Drop Calculator asks for the following values (4): Current (A), Cable length one-way (m), Resistance (Ω per km), Source voltage (V). Fill them in and the result appears immediately — the calculation runs on your own device, so nothing you type is sent to a server.
How accurate is the Voltage Drop Calculator?
The Voltage Drop Calculator uses standard, widely-accepted formulas, so its figures are reliable estimates for everyday planning. They are not a substitute for advice from a qualified professional.
Is the Voltage Drop Calculator free, and do I need an account?
Yes. The Voltage Drop Calculator — and every other calculator on Calculatis — is completely free, with no registration, no download and no limit on how often you use it.