The standard size for one-car garages varies between 12 feet by 20 feet and 14 feet by 22 feet. These units allow space for one vehicle and ample room for storage.
The average size of a two-car garage is 22 feet by 22 feet and can be increased in increments of 2 feet. The larger three-car garage measures 30 feet by 22 feet and most often is built as a stand-alone structure.
Each city within the United States has a maximum square footage allotment that must be adhered to when building a garage. In some cities, permits may also be required before construction can proceed.