Assess your freezer needs. If you have a large family, freeze food from a garden or purchase a large amount of frozen food, you probably need a large-capacity freezer. If your freezing activity is minimal, you probably only require a small freezer.
Multiply the number of people in your household by 1.5 cubic feet of freezer space for a general estimate of freezer space you require. For example, if you have five people in your household, multiply 5 by 1.5 to get 7.5 cubic feet.
Figure that each cubic foot of freezer space holds about 35 lbs. of food. If you regularly purchase large amounts of meat or freeze garden produce, you can determine how much freezer space you require. For example, if you purchase a 250 lb. side of beef, divide 250 / 35 = 7.1 to determine how many cubic feet of freezer space you will need to store the beef.
Add the extra freezer space you require for meat or produce to the general freezer space recommended for your household size. Add a few extra cubic feet for additional freezing space for extra items. Using the same examples, add 7.5 + 7.1 = 14.6 cubic feet. Round this up to 15 and add up to 5 additional cubic feet for a freezer capacity of approximately 20 cubic feet.