The price difference between small and medium storage units is more than $800 per year—even if you use one of the best self-storage companies. That means it pays to estimate the storage unit size you need before renting a unit. Regardless of whether you need temporary storage during a remodel or your garage is bursting at the seams after moving, these five steps could save you hundreds of dollars:

1. Perform an inventory of your belongings
2. Double-check your home storage
3. Calculate your space
4. Pick a small, medium, or large storage unit size
5. Research specific measurements

Bonus: Be sure to check out our list of pro tips on how to save money when selecting a storage unit.

The first step to estimating the storage unit size you need is to see how much stuff you have. Count all of your boxes and identify larger items like couches, tables, and bookshelves. Be sure to write everything down so you can refer back to it later.

For example, if you want to store the contents of a small bedroom in a self-storage unit, your inventory might look like this:

After you’ve inventoried every room, the next step is to make sure you’ve used all of your home’s available storage space. The last thing you want is to pull the trigger on a storage unit, only to realize you could have purchased a smaller (and cheaper) one by storing some of your things in a partly empty closet or an unused corner of your garage.

The difference between a small and medium-sized storage unit is about $840 per year, so it’s worth taking five minutes to double-check your options.

The third step to estimating the storage unit size you need is to measure your belongings. When you pick a storage unit size in Step 4, you’ll want to have one of two measurements:

1. Square feet (sq. ft.). Multiply the length and width of your belongings. If they make a pile that’s 5 x 5 feet, you’d need a storage unit with at least 25 square feet (Extra Space Storage has excellent 5 x 5 storage units).
2. Cubic feet (cu. ft.). Multiply the length, width, and height of your belongings. If your larger items make a pile that measures 5 x 5 x 5 feet, you’d need a storage unit with at least 75 cubic feet.

There’s no one right way to measure your stuff. One approach is to put all your things into a pile and measure the stack to determine your storage need. Another option is to individually measure each item’s length, width, and height. Anything works so long as you have an estimate of your square or cubic footage for the self-storage unit. For help calculating measurements in feet, check out our guide to measuring linear and square feet. 

After you measure everything, determine whether you need a small, medium, or large unit. There are dozens of storage unit sizes, but they all boil down to these three categories. Small units hold up to 50 square feet of belongings, medium units cap out at 150 square feet, and large units can fit as much as 300 square feet.

Some companies like CubeSmart also have extra-small units called storage lockers.  These are ideal if you live in a big city and have a storage need for things like boxes, holiday decorations, and winter clothing.

The easiest way to pick an initial size is to compare your measurements from Step 3 with the Move.org storage unit size guide above. For example, if your inventory measurements equal 125 square feet, you’d want a medium storage unit because its size range is 75–150 square feet.

The fifth step to estimating the storage unit size you need is to check with storage facilities and pick an exact size. You can save money by choosing a unit big enough to store your larger items—but not so huge that you have lots of leftover space.

In Step 4, you narrowed down your options to a small, medium, or large unit. Now, you want to look at storage unit websites to get more specific measurements and see what the companies say will fit (they all have slightly different recommendations).

We recommend checking with our top storage unit companies in your area.

Estimating the storage unit size you need will save you time and money. It’s a hassle to rent a unit and discover it’s not big enough for your boxes and larger items. And it’s no fun to realize you must dish out an extra $70 per month for a storage space that’s half-empty after you fill it up. If a small 5 x 5 storage unit is big enough for your belongings, there's no need to pay extra. 

Here are some tips to make picking a storage unit size easier—and cheaper:

• Compare the costs. Storage units often cost more than your stuff. For example, if you rent a unit to store a dresser, queen bed, and a few bookshelves, it will probably cost about $160 per month—or nearly $2,000 per year. At some point, it’s cheaper to rebuy everything later than it is to store it. Of course, that’s not helpful if you need to store irreplaceable items like yearbooks or legal documents. But you’d be surprised how often people spend more on storage units than their belongings are worth.
• Identify your largest items. Sometimes you don’t have time to create a detailed inventory. Another option is to quickly estimate whether you need a small, medium, or large unit by identifying your longest and widest items. According to the Move.org storage unit size guide, anything over 10 feet long or wide rules out a small unit, while items over 15 feet bump you from a medium- to a large-sized unit.
• Visit a storage facility. You can read all the storage unit guides in the world, but nothing’s as good as the real thing. Take an hour to visit a nearby storage facility. Go inside a few units and get a feel for how big they are and how many boxes will fit. A one-hour visit could save you hundreds of dollars.
• Ask about specific sizes. Many storage unit companies have more available sizes than those published on their website. Call nearby storage facilities, give them your estimated square or cubic footage, and ask which units most closely match your needs. It’s like asking a shoe store to check in the back for your exact size. You could end up with a perfect fit.
• Talk to several companies. Just because a storage unit facility has a medium-sized unit doesn’t mean that you can rent it. In many cases, tenants already occupy the spaces you want. But that’s not the end of the road. Search for storage unit companies near your zip code and check out their online sales. Chances are you’ll find the unit you need.
• Consider moving containers. Don’t forget about portable storage options if you need only short-term storage. Most people use moving containers as a cheap alternative to rental trucks, but you can also store them at your home for a monthly fee. You may be able to save some money—and the headache of transporting your belongings to and from the storage facility.

The average square footage of a 3-bedroom house is approximately 1,200–1,400 square feet, according to Reference.com.¹ Move.org recommends a medium-to-large-sized storage unit for the contents of a three-bedroom home.

A 5 x 5 storage unit is 5 feet long and 5 feet wide (or 25 square feet). The average cost for one of these small storage spaces is approximately $90 per month.

A 10 x 10 storage unit is 10 feet long and 10 feet wide (or 100 square feet). The average cost for one of these medium-sized self-storage units is approximately $160 per month.

Storage units range from 3 x 3 feet (small) to 10 x 30 feet (large). In some cases, you can find units up to 50 feet long designed for oversized recreational vehicles. Prices vary, but you typically pay more for larger storage spaces than smaller ones.

The average storage unit size is approximately 10 x 10 feet (or 100 square feet). These medium-sized units cost around $160 per month and can often fit belongings from 1 to 3 bedrooms.

The size of the storage unit that you need depends on how much stuff you have. Move.org recommends you calculate the square footage of your belongings and then choose between a small (25–50 square feet), medium (75–150 square feet), or large (200–300 square feet) storage unit.

The largest standard storage unit size is 10 x 30 feet. These large units hold a capacity of 300 square feet (or 2,400 cubic feet) and cost approximately $290 per month.

You can find 10 x 10 storage at any major storage facility. Move.org recommends Extra Space Storage, CubeSmart, and Simply Self Storage.

The average cost of a 5 x 5 storage unit is approximately $90 per month. These small 25-square-foot units often fit many belongings from one small bedroom.

Simply Self Storage has the most affordable storage space. Move.org says its average monthly price of approximately $160 is about $20 below the industry average.

You typically need a medium- or large-sized storage unit for major appliances. While most storage unit companies recommend large units for major appliances, you can often fit items like refrigerators, washers and dryers, and fridges in medium-sized units.

The amount of furniture you can fit in a storage unit depends on the size of your self-storage space. For example, most couches are over seven feet long—or longer than many small storage units. Move.org recommends you compare the dimensions of your furniture with the measurements of your storage unit to estimate how much will fit.

Yes, a mattress set will usually fit in a medium storage unit. Move.org recommends you compare the size of your mattress set with the dimensions of your storage unit.

The smallest storage unit size is a storage locker that ranges from 9–25 square feet. They’re generally large enough to fit a few boxes and an end table.

Yes, you likely need climate-controlled storage for document storage. Climate-controlled storage prevents damage to valuable documents and photographs by monitoring your unit’s humidity and temperature levels.

Valuable business storage files should be kept in a space more secure than a storage unit (like a company warehouse). However, you can lower your business storage files risk by asking employees to sign a log each time they access your storage unit.

A storage locker is smaller than a 5 x 5 storage unit. However, these extra small self-storage spaces can be hard to find (CubeSmart and U-Haul are your best bets). 

• Best Professional Movers
• Best Self-Storage Companies
• What to Know Before Renting a Storage Unit
• How to Store Clothes in a Storage Unit
• What to Know About Climate-Controlled Storage

• How Much Does a Storage Unit Cost?
• What Can (and Can’t) I Store in a Storage Unit?
• Do I Need Insurance for My Storage Unit?
• How Do Storage Auctions Work?
• What Should I Know Before Renting a Storage Unit?

1. Reference.com, “What Is the Average Size of a Three-Bedroom House?” April 14, 2020. Accessed June 9, 2022.