Last updated: May 2026
The number one mistake people make when renting their first storage unit is going too big “just to be safe.” It feels like the smart play. It’s actually the most expensive way to over-pay every month for empty air. The number two mistake is going too small to save $20, then realizing on move-in day that your couch doesn’t fit and you need a second unit.
This guide walks through which storage unit size you actually need based on what you’re storing. It uses real-world room counts and furniture lists from a working WNY storage facility, not generic industry estimates. By the end, you’ll know whether you need a 5×5 or a 10×20 before you ever pick up the phone.
How storage unit sizes work
Storage units are described by their floor dimensions in feet: 5×5, 5×10, 10×10, 10×15, 10×20, 10×30, and the larger sizes. Standard ceiling height is usually 8 feet, sometimes 10. That ceiling matters more than people realize, because most of your stacking happens vertically.
A 5×5 unit gives you 25 square feet of floor and roughly 200 cubic feet of usable storage. A 10×10 quadruples the floor and gives you about 800 cubic feet. A 10×20 doubles that again to roughly 1,600 cubic feet. You can think in square feet for floor planning, but think in cubic feet for what fits.
At Jeff’s Attic across our WNY locations, we run sizes from 5×5 up to 10×30 and larger, with specific availability varying by Niagara Falls, Grand Island, and Wheatfield.
Size-by-size guide: what fits where
Here’s what each common size actually holds, based on what our staff sees customers fit in real units (not what a stock-photo industry guide claims).
| Unit Size | Square Feet | Comparable Space | What Typically Fits |
|---|---|---|---|
| 5×5 | 25 sq ft | Small closet | Boxes, lamps, small chair, seasonal gear, motorcycle (with care) |
| 5×10 | 50 sq ft | Large walk-in closet | Contents of one small room: chair, sofa, chest of drawers, lamps, boxes |
| 10×10 | 100 sq ft | Half a one-car garage | Contents of one full bedroom or studio apartment |
| 10×15 | 150 sq ft | One-car garage | Contents of 2 to 3 small rooms with furniture |
| 10×20 | 200 sq ft | Full one-car garage | Contents of a 2 to 3-bedroom apartment, or a small house |
| 10×30 | 300 sq ft | One-and-a-half car garage | Contents of a 3 to 5-bedroom house, larger vehicles |
The 5×5 is the smallest unit and is right-sized for a college student, an apartment downsize, or a single-room declutter. If you’ve got more than 30 medium-size boxes, you need to go larger.
The 5×10 is what most first-time renters actually need but don’t think to ask about. It holds one full bedroom’s worth of furniture and boxes. If you’re storing the contents of a guest room or doing a small apartment swap, this is usually the size.
The 10×10 is the workhorse size in WNY. It’s the most rented unit at most facilities, including ours, because it covers a one-bedroom apartment, a small office, or a major garage cleanout.
The 10×15 is the upgrade size when 10×10 is just barely too small. Two bedrooms with furniture, or one bedroom plus a fair amount of garage.
The 10×20 is what you rent when you’re storing a whole household between moves, doing a major renovation, or relocating. It’s also the size most people overshoot to “just to be safe,” when a 10×15 would do.
The 10×30 is the bigger size for true full-house storage or for storing vehicles alongside household goods.
How to size a unit by room count
The cleanest way to size a unit if you don’t want to inventory box-by-box: count the rooms whose contents are going into storage, including the major furniture from each.
- 1 small room (guest bedroom, home office): 5×10
- 1 full bedroom with bed, dresser, nightstand, plus 10 to 15 boxes: 5×10 to 10×10
- 1-bedroom apartment (kitchen, living, bedroom, bath): 10×10
- 2-bedroom apartment: 10×10 to 10×15
- 3-bedroom house: 10×15 to 10×20
- 4-5 bedroom house with full contents: 10×20 to 10×30
- Full house contents including appliances, large furniture, and garage: 10×30 or larger
This is the same math our staff walks first-time renters through when they call (716) 773-2000. It works for about 80% of typical situations. The remaining 20% are the special cases below.
Special cases that change the math
Standard sizing assumes standard furniture and a reasonable amount of stuff per room. A few situations change the calculation:
Pianos, pool tables, or oversized furniture. A baby grand piano alone takes up most of a 5×10. A pool table needs a full 10×10 just for itself, ideally on its side. If you’ve got one or two pieces like this, bump up at least one size from the room-count guidance.
A lot of books or paper records. Boxes of books are heavy and you can’t stack them as high as you might think (the boxes on the bottom collapse). Plan for less vertical stacking and more floor space.
Long items. Skis, surfboards, ladders, lumber, large mirrors. The 5×5 won’t fit anything over 5 feet diagonally, so a 5×10 minimum is what you need for long items.
Vehicles included. Storing a motorcycle alongside household goods? Add a 5×10 of footprint to whatever room count you were planning, and consider vehicle storage at Jeff’s Attic for cars, boats, and trailers separately rather than mixing.
Climate-sensitive items. Electronics, wood furniture you’ve invested in, artwork, anything with finish or moisture-sensitive components. Standard storage works for almost everything in WNY, but if you’re storing a piano or a valuable instrument long-term, the conversation gets longer. Call before you commit.
Frequent access. If you’ll need to get into the unit weekly and pull specific items, you need walking-aisle space inside the unit. Add 25% to your calculated size to leave aisles, or go up one size from where the room count puts you.
How to avoid renting too much (or too little)
The two most useful sizing tactics:
Pack boxes before you measure. Most people guess box count low. They imagine “maybe 20 boxes” and end up with 45. Pack everything first, count the boxes for real, and then size the unit. This is the single biggest accuracy improvement.
Use the cubic feet calculation, not just floor. 100 boxes at 1.5 cubic feet each is 150 cubic feet, which fits comfortably in a 5×10 (200 cubic feet) if stacked well. People often book a 10×10 (800 cubic feet) for what could fit in a 5×10, because they think in floor area instead of stacking space.
Call before you book. Our staff at Jeff’s Attic walks through this sizing conversation a few dozen times a week. Five minutes on the phone with a list of major items gets you a much better answer than guessing online. Call (716) 773-2000.
What to do if you’re between sizes
If room count puts you between 10×10 and 10×15, the right call usually depends on three things:
How long you’ll need it. For short storage (1 to 3 months), squeeze into the smaller size and pack tightly. For long storage (6+ months), pay for the larger size so you can access things without unpacking everything.
How often you’ll access it. Frequent access means you need aisle space inside the unit, which means upsize. Drop and forget means downsize and pack to the ceiling.
Your price sensitivity. The price difference between a 10×10 and 10×15 in WNY is usually $20 to $40 per month. Over six months, that’s $120 to $240. Worth it if access matters, not worth it for short-term drop and forget.
When in doubt, slightly larger beats slightly smaller. Splitting your stuff across two units because you went too small costs more than upsizing by one tier from the start.
Frequently asked questions
What’s the most common storage unit size people rent?
The 10×10 is the most rented size at most WNY facilities, including Jeff’s Attic. It holds a one-bedroom apartment’s worth of contents, fits a half-garage cleanout, and works for a small office relocation. It’s the right answer for a wide range of situations, which is why it’s the most popular.
How tall are storage units?
Standard storage unit ceilings are usually 8 feet, sometimes 10. Always ask the specific facility, because this affects how high you can stack and therefore how much actually fits. A 10×10 with a 10-foot ceiling holds 25% more than one with an 8-foot ceiling.
Can I fit a car in a storage unit?
Yes, in larger sizes. A 10×20 fits most standard cars. A 10×30 fits larger vehicles or vehicles plus some household goods. But for car-only storage, dedicated vehicle storage is usually a better and cheaper option than renting a unit large enough to drive into. Jeff’s Attic offers dedicated vehicle storage for that exact reason.
Should I rent a larger unit just to be safe?
No, but rent slightly larger if you’re between two sizes and you’ll need it for 6+ months. The “just to be safe” upgrade two sizes up is the single most common over-spend pattern in storage. The 5% of people who genuinely need more space will know it from packing the boxes. The other 95% are paying extra for empty air.
What size storage unit do I need for an apartment move?
Studio or 1-bedroom: 5×10 to 10×10. 2-bedroom: 10×10 to 10×15. 3-bedroom: 10×15 to 10×20. These ranges assume standard furniture and average possessions. Pack the boxes first to confirm, and call to verify before booking.
Can I switch sizes if I get it wrong?
Usually yes. At Jeff’s Attic, customers can move to a larger or smaller unit if availability allows, often without much hassle. Talk to the team at (716) 773-2000. Better to size right the first time, but it’s not a permanent commitment.
Pick the right size the first time
Storage unit sizing isn’t complicated once you know the categories. Count the rooms, pack the boxes first, account for any oversize items, and either match the size-by-room chart or upsize one tier if access matters. That gets you to the right answer for almost every situation.
If you want a second opinion before booking, call (716) 773-2000 and the team can size your situation in a few minutes. We hold any size unit for up to 30 days with no payment upfront, so you can reserve, double-check your boxes, and adjust before move-in if needed.
Find availability at the Niagara Falls, Grand Island, or Wheatfield location, or check current pricing at the main storage units page.
About the Author
Jeffrey Williams is the owner of Jeff’s Attic Secure Self Storage, a BBB-accredited (A+) self storage business operating in Western New York since 2014. He also owns Apartments Niagara LLC, managing over 700 residential units across Niagara Falls, Grand Island, Lewiston, Buffalo, and the Town of Niagara. Over a decade of helping local residents size storage units for moves, downsizes, and military deployments has shaped how Jeff and his team approach the sizing conversation: practical, no over-selling, and built around what people actually have to store.