As a guide, you can use the chart below to determine what is the best size storage unit for you.
A 5x10 is like a walk-in closet. You can fit studio apt. or small bedroom furnishings, mattress set, dining room
A 10x10 is like a small bedroom. You can fit 1-2 bedroom apt. furnishings, refrigerator, appliances, canoes, sofas
A 10x15 is like a small office. You can fit 1-2 desks, cabinets, large printers, chairs, sofas
A 10x20 is like a large bedroom. You can fit 1-2 bedroom home furnishings, refrigerator, appliances, canoes, sofas
A 10x30 is about the size of large 1 car garage. You can fit 2-3 bedrooms of furniture appliances, good for business storage