A 5x10 storage unit is the size of a small walk-in closet.
It fits furnishings of a mid-sized bedroom, including a queen-sized bed, a TV and several small to medium-sized boxes.
A 10X10 is the size of 1/2 of a standard one car garage. Generally a 10X10 can hold the contents of two bedrooms and several small boxes.
A 10x15 storage unit is a little smaller than a standard one-car garage.
It can fit the contents of three full bedrooms OR larger items such as a piano, couches, tables, or large-screen TVs, plus several medium to large-sized boxes.
A 10x20 storage unit is the size of a standard one-car garage.
It can fit the contents of a multi-bedroom house, including several oversized items like a couch, a refrigerator, a washer/dryer or several large boxes.
A 10x30 storage unit is as large as a 1 ½ car garage.
It fits the contents of a fully furnished 3 bedroom house, including oversized items such as a couches, beds, dressers, a refrigerator, a washer/dryer, a dining room set, an entertainment center and several large boxes.