Storage Unit Size Guide: How to Pick the Right Size Without Overpaying

Most people rent a storage unit that is at least one size too big, and end up paying for empty square footage every month. Picking the right size comes down to matching unit dimensions to what you actually own, not guessing off a chart. This guide walks through the common sizes, what they realistically hold, and how to avoid the sizing mistakes we see most often in Savannah.

What Size Storage Unit Do I Need?

For most one to two bedroom households, a 10x10 unit is the right starting point. Studio and one-bedroom apartments usually fit in a 5x10, while three to four bedroom homes typically need a 10x20 or larger. The fastest way to size correctly is to count rooms first, then adjust for anything oversized like a sectional, a piano, or several boxes of seasonal gear.

Unit sizes are sold in rough square footage, but what actually matters is usable volume: most facilities allow stacking to 8 feet, so a smaller footprint packed to the ceiling can hold more than a larger one packed loosely at waist height.

5x5 and 5x10 Units: Small Apartments and Overflow

A 5x5 unit is closet-sized, good for seasonal decorations, a few boxes, or sporting equipment. A 5x10 is closer to a walk-in closet and comfortably holds the contents of a studio or small one-bedroom apartment, including a mattress, a few boxes, and small furniture pieces stood on end.

10x10 Units: One to Two Bedroom Homes

A 10x10 is the most commonly rented size because it covers a typical one or two bedroom apartment without waste. It holds a sofa, a bedroom set, a dining table, appliances, and 20 to 30 medium boxes when packed with some thought given to stacking.

10x15 and 10x20 Units: Full Households

A 10x15 suits a two to three bedroom home, and a 10x20, roughly the size of a one-car garage, is where most three to four bedroom households land. If you are storing everything from a full move rather than just overflow, plan on one of these two sizes rather than trying to squeeze into a 10x10.

How Do You Estimate Storage Size Without Guessing?

The most reliable method is to walk through your home room by room and note large furniture, then add roughly 15 to 20 boxes per room for a lived-in household. Facilities and moving companies often have size calculators, but a room count plus a furniture list gets you close enough to book with confidence.

If you are storing during a move rather than long term, it helps to think in terms of your moving truck size. A unit close in size to the truck you would need for the same items is usually the right match.

5x10 vs 10x10 Storage Unit: Which One Actually Saves Money?

A 5x10 costs less per month, but if your belongings do not fit, you either pay for a second unit or make return trips, both of which cost more than renting the larger size once. The safer move when you are between two sizes is almost always to size up, since unused space costs far less than a second rental or a wasted trip.

The exception is short-term storage during a move with a tight, known inventory. If you have already done a room-by-room count and it clearly fits a 5x10, there is no reason to pay for a 10x10.

What Common Mistakes Lead to Renting the Wrong Size?

The biggest mistake is estimating based on room count alone without accounting for how furniture actually stacks. A sectional sofa, mattress, and dresser take up far more floor space than boxes, so heavy-furniture households need to size up even if the room count suggests a smaller unit.

The second common mistake is forgetting an access aisle. You need to be able to walk in and reach items in the back, so a unit "technically" large enough on paper can still feel cramped in practice. Leave roughly 20 percent of the unit as walking space when you plan your layout.

Packing Smart to Make a Smaller Unit Work

Uniform box sizes stack far more efficiently than mismatched boxes, which is often the difference between fitting in a 10x10 and needing a 10x15. Disassembling bed frames and table legs, storing mattresses on end in a mattress bag, and filling drawers with soft items instead of leaving them empty all reclaim usable space without needing a bigger footprint.

Good packing supplies make this easier: matched box sizes and sturdy dollies let you build tight, stable stacks instead of leaving gaps that waste cubic footage. If you are unsure how long you will actually need the space once it is packed, our guide on how long to keep a storage unit before moving everything in can help you avoid paying for months you do not need.

Getting the Right Fit the First Time

Sizing a storage unit correctly saves money twice: once by avoiding an oversized rental, and again by avoiding the cost of a second unit or extra trips when a small one turns out too tight. Count rooms, list large furniture, leave room for an access aisle, and size up when you are genuinely on the fence.

If you would rather have someone assess your inventory directly, our team can help you size and book the right unit as part of a move. Explore our climate-controlled storage services in Savannah, or contact BC Brothers Moving to talk through your specific situation.