Wire voltage drop
Formulas, limitations and content checked according to our Editorial method.
Quickly size a DC, single-phase or three-phase connection from current, one-way length and conductor area.
Calculate
Resistance
—
Drop
—
Loss
—
Power loss
—
Worked example
At 12 V and 10 A, a 5 m one-way copper cable with a 2.5 mm² area drops about 0.69 V, or 5.7%.
Calculation limits
The result uses nominal resistivity at 20 °C and excludes reactance, temperature, connections and installation codes. Mains wiring requires professional verification.
Frequently asked questions
Is the entered length one way?
Yes. For DC and single-phase circuits the calculator automatically includes the outgoing and return conductors.