How to Choose the Correct Wire Gauge for Your Extension Cord

Locate the required wattage of the electronic device normally located at the bottom or back.

Calculating the correct gauge

  1. Calculate the total wattage of all your devices.
  2. Divide by 110 (the standard household voltage )
  3. Round down to the nearest whole number

The result is the cord gauge that you need. 

Example
Total wattage = 1200W / 110 = 10.9
Round down = 10 Gauge.

Most devices will do fine with 12 gauge extension cords. Power hungry devices such as lawnmowers, heavy machines, require a lower gauge such as 10AWG. Keep in mind, the lower the gauge means the thicker the cord.