# How to Calculate a Duty Cycle Many electrical devices do not operate continuously but instead have a discrete amount of time during which they are active and then a certain amount of time when they are inactive. The duty cycle of a machine is defined as being a quantitative measure how long a machine is on relative to how long it is off. A refrigerator is an example of a machine that has a duty cycle.

The duty cycle of a machine can be calculated using a very simple formula and a calculator.

1. Use the timer to determine the length of time the machine is switched on. Take a note of this value. For example, a refrigerator pump may be on for approximately 30 minutes.

2. Time the period in which the machine is switched off. Take a note of this value. Following the example, a refrigerator pump may be off for approximately 10 minutes.

3. Calculate the duty cycle using the following formula:

4. Duty Cycle = 100 * (Time on ) / (Time on + Time off)

5. Following the example leads to a duty cycle of:

6. Duty Cycle = (30 minutes) / (30 + 10 minutes) = 30/40 = 75 %