Select conductor size from current, run length and voltage drop limit.
Single phase circuits count the run twice because current returns along the neutral, while three phase uses the square root of three. Long runs are usually governed by voltage drop rather than by ampacity. A cable sized only for its current rating can still deliver unacceptable voltage at the far end, which is why drop is the binding constraint on anything beyond a short run.
Wire Size
Area = k × ρ × L × I ÷ allowable drop, where k is 2 single phase and 1.732 three phase
Area = k × ρ × L × I ÷ allowable drop, where k is 2 single phase and 1.732 three phase Single phase circuits count the run twice because current returns along the neutral, while three phase uses the square root of three. Long runs are usually governed by voltage drop rather than by ampacity.
A cable sized only for its current rating can still deliver unacceptable voltage at the far end, which is why drop is the binding constraint on anything beyond a short run.
This calculator takes 5 inputs: Load current, One-way run length, Supply voltage, Maximum voltage drop, Circuit type. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.