In need of a 5x10 storage unit? Extra Space Storage offers 50-square-foot self storage units with a range of amenities that can accomodate your storage needs. How big is a 5x10 storage unit? 5x10 units are comparable to a mid-sized walk-in closet. These self storage units offer 50 square feet of storage space, providing plenty of room for small storage needs. What can be stored in a 5x10 storage unit? A 5x10 storage unit can hold the contents of a studio apartment, dorm room, or mid-size bedroom