Kristy, according to the Better Homes and Garden website the method is Watts/Voltage=Amperage, so if you've got a total load on a 120 Volt circuit of 2400 Watts that would equal 20 Amps (2400/120=20). So a 20 Amp breaker can handle a total load of 2400 Watts, a 15 Amp breaker would handle a total load of 1800 Watts, and so on. Hope this helps!