Voltage Drop Basics for DIY Circuit Planning
Every conductor is a small resistor. Over distance, load current turns that resistance into lost volts at the device. This guide explains the worksheet formula without treating it as stamped engineering.
Why percent matters
A 3 V drop is minor on a 240 V circuit (~1.25%) but harsh on a 12 V DC run (25%). Always normalize drop to source voltage.
One-way length
Enter the distance to the load once. Single-phase formulas already include the return conductor via the factor of 2.
Related energy cost tools
Voltage drop wastes a little energy as heat in the cable. For bill estimates from watts and hours, use the published home-utilities calculators.