We typically suggest the following guidelines:
5 x 5 Can hold items from one small room. Items such as small beds, chest of draws, chairs, desk, or small boxed items.
5 x 10 Can hold items from a small one bedroom apartment. A bed, sofa and boxes.
5 x 15 Can hold items from a typical sized one bedroom apartment. Bed, sofa, living room furniture, and boxes.
10 x 10 Can hold items from a one or two bedroom apartment. Beds, sofa, living room furniture, many boxes, washer, dryer.
10 x 20 Can hold items from a three or four bedroom apartment or house. Many boxes, appliances, beds, sofa, etc.