Power Cable Calculator

The purpose of this calculator is to help you determine which wire and voltage to use on a low voltage lighting system for optimum performance. Step #1 - Input the voltage of your existing or new power transformer:11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 or 24 volts Step #2 - Input the total length of your wire from the transformer to each branch circuit Step #3 - Plug in the total wattage of your individual branch circuits Step #4 - Select a drop multiplier: 1, 1.5 or 2

When most of your lights are at the far end of the run, use the 1.5 multiplier.This is very important!


You choose: 0 Voltage, 0 Feet, and 0 Wattage, with a 0 drop multiplier.

Minimum Cable Constant =

Online Power Cable Calculator

Power Cable Chart

Always start your calculations with 12-gauge wire. The voltage at a fixture is the actual voltage supplied (12 Volts) minus the voltage drop. The voltage supplied may be increased by use of a multi-tap transformer. These multi-taps have alternate voltage sources to counteract a long cable run with too high of a voltage drop. Another way to counteract a high voltage drop is change to a thicker wire, such as 10-guage. If you need more voltage drop than you are getting, you may change to a thinner wire, such as 14-gauge, but a thinner wire supports less wattage.

Here is a chart to determine the maximum wattage allowed for each buried wire.

Gauge #18 GA #16 GA #14 GA #12 GA #10 GA #8 GA
Max Wattage 120 W 156 W 180 W 240 W 300 W 480 W