Measuring your microwave oven's size in cubic feet will give you its volume. The amount of cubic feet inside your microwave is an indicator of how much food it can hold. Most microwaves range from 1 to 2 cubic feet, although some may be larger or smaller depending on the model. To determine the microwave's interior capacity, always take measurements from the inside. If you need to know how much space the entire microwave will use, take measurements from the outside.
Measure the height of the microwave. For example, your microwave is 11 inches high. Record this number on paper.
Measure your microwave's width. For example, your microwave is 18 inches wide. Record this number.
Measure your microwave's depth. For example, your microwave is 12 inches deep. Record this number.
Multiply all three of the numbers you have recorded. In our example, 11 times 18 times 12 equals 2,376.
Divide the product of the three dimensions by 1,728 to convert inches to feet. In our example, 2,376 divided by 1,728 equals 1.375, or approximately 1.4. This is the volume of the microwave in cubic feet.