DC Voltage Drop Calculator
Estimate voltage drop in a two-wire DC circuit using current, one-way cable length and conductor resistance per 1,000 feet. The calculator also reports percent drop and estimated load voltage.
Resistance-based DC estimate. Actual conductor resistance changes with material, size and temperature.
How this tool works
DC loop voltage drop = 2 × current × one-way length × resistance per 1000 ft ÷ 1000.
Example
A 20 A load 100 ft from a 24 V source with 1 Ω/1000 ft conductor resistance produces a 4 V loop drop, or about 16.7% of source voltage.
Common questions
Why is length multiplied by two?
Current travels out to the load and returns through the second conductor, so the resistive loop length is twice the one-way distance.
Does resistance change with temperature?
Yes. This simplified calculator uses the resistance value you enter and does not automatically correct it for temperature.