Like other kitchen appliances, ovens are available in many sizes to suit your room, lifestyle and cooking habits. Just as the external dimensions vary, so do the dimensions of the cooking space itself. Generally, the more insulated the oven is, the smaller the cooking area becomes, so outward size is not always a guide to cooking capacity. Establishing the cubic feet of cooking space within your oven requires nothing more than a tape measure and simple multiplication.
Check the oven and be certain that it is switched off and cold. If there is even a slight risk of somebody switching it on, be safe. Disconnect an electric oven from the power supply and turn off the gas supply to a gas oven. Remove portable shelving and other items to leave the oven space as empty as possible.
Measure the depth of the oven, from the back to the door lip, and record this value in inches. Measure the width and the height and again record the dimensions in inches.
Multiply the width by the height and depth to obtain the oven volume in cubic inches. For example, an oven with a depth of 20 inches, a width of 20 inches and a height of 30 inches has a capacity of 12,000 cubic inches -- 20 x 20 x 30 = 12,000.
Divide the capacity in inches by 1,728, the number of cubic inches in 1 cubic foot. The result is the capacity of the oven expressed in cubic feet. To conclude the previous example, an oven with a 12,000-cubic-inch capacity has a 6.94 cubic foot capacity because 12,000 divided by 1,728 equals 6.94.