There are many ways and ideas to judge the proper size unit for the things you're looking to store. Below are a few visuals that may help and are presented for reference purposes only.
Many things will affect how much you can store but some that top the list include how well you pack things, type of containers used, size and shape of items being stored and how efficiently you're able to position and stack your belongings.
We hope the following visuals help (Play the videos, the longest is 11 seconds):
5 x 10 => (50 sq-ft) Similar to a larger walk in closet. Ideal for the contents of a small studio type apartment including several boxes, kitchen appliances, small mattress set, chairs, smaller entertainment center, motorcycle and alike.
10 x 10 => (100 sq-ft) Equal in size to half of a one-car garage. Sized right for a one bedroom apartment including a large mattress set, appliances, dining set, chairs, couch, sporting equipment, bicycles and alike
10 x 15 => (150 sq-ft)Size equivalence to a typical 2 bedroom space. Great for large screen TV's, couches, outdoor furniture, dining room set, appliances, mattress sets and more.
10 x 20 => (200 sq-ft) This larger sized unit is the size of a one-car garage and will store three bedroom equivalence including lawn and garden items, multiple appliances, mattress sets, furniture and much more. Ideal for Business Storage as Well!
10 x 30 => (300 sq-ft) This big daddy is like a two-car garage and is our largest! This one will typically store the contents of an entire home. Ideal for relocating purposes or Business Storage as Well!