How to Calculate Circuit Breaker Trip Settings

Each circuit breaker in your breaker panel is labeled with the maximum amperage (current) capacity for that circuit. This may differ among circuits, so always check each breaker's capacity individually when calculating the electrical load that will cause that breaker to trip. Standard household circuits in the U.S. are 120 volts, but some circuits have double that capacity for appliances such as stoves and air conditioners. These breakers have 240-volt capacities and will be approximately twice the size of 120-volt breakers. Wattage is the easiest measure of power load to calculate and monitor so you don't accidentally trip your breakers.

Step 1

Look for the amperage notation on the breaker switch. This will generally be 15 or 20. Also look for the voltage notation, which may be on the breaker switch as well, and will be 120 or 240. If you cannot locate the voltage, assume that breakers that take up one panel slot are 120 volts and breakers that take up two slots are 240 volts.

Step 2

Multiply the amps by the volts. In most circuits, this will be 20 x 120 = 2400 or 15 x 120 = 1800. The number resulting from this equation is the maximum wattage load you can place on the circuit before tripping the breaker.

Step 3

Apply the same calculation to 240-volt circuits. For example, a 240-volt circuit with a 30-amp capacity would allow 7200 watts (30 x 240 = 7200).

Step 4

Check the wattage for all electrical fixtures and appliances on the circuit. If the total wattage is over your maximum calculation, the breaker will trip.


Anne Hirsh

Anne Hirsh has been writing and editing for over 10 years. She has hands-on experience in cooking, visual arts and theater as well as writing experience covering wellness and animal-related topics. She also has extensive research experience in marketing, small business, Web development and SEO. Hirsh has a bachelor's degree in technical theater and English and post-baccalaureate training in writing and computer software.