The load capacity of an electrical circuit in an appliance measures the amount of power that flows through that circuit at one time. Just because an appliance is on doesn't necessarily mean that circuit is operating at capacity. Often, capacity is a little higher than normal to prevent power surges and blown fuses in your home. Load capacity of a circuit uses a math formula and measures in "amps."

Step 1

Find out if the circuit is a "single phase" or "three phase" circuit by looking at the documentation that came with the device. This information affects the mathematical formula to calculate load capacity properly.

Step 2

Write down the number of volts and the number of watts used in the circuit. If the circuit is in an appliance or a circuit breaker in your home, for example, this information is on the documentation that came with the device, if not listed on the actual device itself.

Step 3

Multiply the number of volts by 1.732 for a three phase circuit only. If you are calculating with a single phase circuit, skip this step.

Step 4

Divide the number of watts by the number of volts for your circuit. If using a three phase circuit, divide the number of watts by the number you received in "Step 3." The number you get is the load capacity, in amps, for the circuit.