Calculate voltage drop along a cable and check it against the permitted limit.
Voltage drop is proportional to current, length and resistance per metre. Single-phase circuits incur twice the drop of the one-way calculation because both conductors carry current, while three-phase uses the √3 factor instead. Long circuits are usually sized by voltage drop rather than current-carrying capacity, which is why the maximum-length figure is the practical design output.
Cable Voltage Drop
Single phase: ΔV = 2 I R L; three phase: ΔV = √3 I R L
Single phase: ΔV = 2 I R L; three phase: ΔV = √3 I R L Voltage drop is proportional to current, length and resistance per metre. Single-phase circuits incur twice the drop of the one-way calculation because both conductors carry current, while three-phase uses the √3 factor instead.
Long circuits are usually sized by voltage drop rather than current-carrying capacity, which is why the maximum-length figure is the practical design output.
This calculator takes 6 inputs: Design current, Cable route length, Conductor cross-sectional area, Nominal voltage, Phases, Permitted voltage drop. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.