How this calculator works
This page fixes source voltage at 220 V and models two conductors supplying a DC or unity-power-factor single-phase load. The metric-size table converts the chosen percentage drop into maximum lengths for areas from 1.5 to 50 mm². Copper and aluminium use representative 20 C resistivity and alpha = 0.0039/K; custom material properties are also available. Bare-wire diameter is calculated from area, so it excludes insulation. A nominal 220 V label does not describe every local supply. Use the actual supply voltage in the general calculator when it differs, and check thermal capacity and local wiring requirements independently.
Formula
DeltaV = k rho(T) L I/A; A = k rho(T) L I/DeltaV; L = DeltaV A/(k rho(T) I); I = DeltaV A/(k rho(T) L). For two wires k = 2; for balanced three-phase k = sqrt(3). rho(T) = rho20[1 + alpha(T - 20 C)].
Worked example
At 220 V, a 3% allowance is 6.6 V. A 20 A load 30 m away requires 3.05455 mm² of copper at 20 C by voltage drop. A 2.5 mm² copper conductor at 10 A reaches the same 3% limit after 49.1071 m one-way.
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Frequently asked questions
Can I use this for a 230 V or 240 V supply?
Use the general wire size calculator with that voltage. This focused page keeps 220 V fixed so its metric-size table has a consistent reference.
Are the table lengths permitted installation lengths?
They satisfy only the entered resistance-based drop limit. Thermal limits, protection, installation method and equipment terminals can impose tighter constraints.
Does this cover a motor with low power factor?
The two-wire model assumes resistive voltage drop and omits cable reactance. A full AC voltage-drop calculation is needed when phase angle matters.