You already know how much stuff you need to put in self storage, so figuring out the unit size you need is the next step. Smaller units such as 5'x5' or 5'x10' spaces can usually be filled with the amount of items you would normally store in a closet: a few chairs and lamps, sports equipment, garden tools and some boxes.Moving on to larger sizes, imagine the 10'x10' and 10'x15' units as similar to a bedroom or a living room – larger pieces of furniture, sturdier equipment and bicycles can fit here. Finally, a 10'x20' unit has enough space for the contents of a 3-bedroom house, while the larger 10'x30' space easily accommodates the contents of a loaded semi-truck.