While you may not often think about the capacity of your freezer, in some cases, the measurement comes in handy. For instance, if you are buying a large quantity of prepackaged meet or storing a catch of fish for a friend, calculating the true number of cubic feet of storage space lets you know if you have enough room to take on the storage task. When it's time to buy a new chest freezer, knowing the capacity of the existing freezer ensures you'll buy one with enough space for your needs -- exterior size alone is not an indication of interior capacity, nor is the manufacturer's claim necessarily accurate.
Remove all the items from within the freezer, or at least push items to the side while taking each measurement.
Measure the depth of the freezer from the bottom to the highest point it can be filled without obstructing the lid. Jot the number down on scrap paper, using feet as a measurement. For instance, 2 feet 6 inches is written as 2.5 feet. Every 3 inches equals 0.25 additional feet -- 9 inches equals 0.75 feet.
Measure the interior width of the freezer from one inner wall across to the other. Jot that number down as well, in feet.
Measure the interior of the freezer from front inside wall to back inside wall. Jot down this measurement in feet.
Multiply the three numbers together to determine capacity of the freezer in cubic feet.