Wire Voltage Drop Calculator
Estimate voltage drop, percentage drop, and power loss in a copper or aluminium wire run from AWG gauge, length, and current.
Wire resistance (round trip)–
Voltage drop–
Percentage drop–
Power lost as heat–
Voltage at load–
Voltage drop in a wire
Every conductor has a small resistance, so current through a long run loses a little voltage as heat before it reaches the load. Drop grows with length and current, and shrinks with a thicker (lower-AWG) wire.
V_drop = I × R, with R = ρ × (2 × length) / area
The length is doubled because current flows out and back. Aluminium has about 1.6× the resistivity of copper, so it drops proportionally more for the same gauge. A common rule of thumb keeps drop under 3% of the supply.
Related
Look up a wire's diameter and area with theAWG wire gauge calculator, or size a PCB track with thePCB trace current calculator.