Common self storage unit sizes run from 5x5 (25 square feet) to 10x30 (300 square feet), with 5x10, 10x10 and 10x15 the usual middle of the range. For an owner, the job is to price each size so rent per square foot falls as the unit gets bigger, and to build or convert a unit mix that matches what local renters actually ask for.
Sizes below are nominal. Real units vary by building, door type and ceiling height, so measure yours.
Size chart
Square feet are length times width. The "what fits" column is a rough guide for renters. Tell them to measure their largest items.
| Size | Square feet | Rough guide to what fits |
|---|---|---|
| 5x5 | 25 | Boxes, seasonal items, small furniture |
| 5x10 | 50 | Contents of a small room, a few large items |
| 10x10 | 100 | Many one-bedroom apartment contents |
| 10x15 | 150 | Two-bedroom contents, or a small business stock |
| 10x20 | 200 | A larger home, or a car plus items |
| 10x30 | 300 | A large home, or larger vehicles and equipment |
Units larger than 10x30, and outdoor spaces for vehicles, are a different product. See RV and boat storage for that.
Why unit sizes matter to you
Your unit mix is how many units you have of each size. See unit mix. It decides:
- What renters can find, and so how quickly you fill.
- How much rent each square foot earns.
- What you can sell at the same time, such as business tenants who want larger units.
If you have too many large units and a town of apartment dwellers, they sit empty. The reverse is also possible.
How to price a size ladder
A size ladder is the list of rents by size. The rule: bigger units cost more per month but less per square foot, since the renter gets a volume discount and larger units are slower to fill.
Worked example (illustrative)
These rents are made up to show the method. They are not a price recommendation. Check your market first.
| Size | Sq ft | Monthly rent | Rent per sq ft |
|---|---|---|---|
| 5x5 | 25 | $45 | $1.80 |
| 5x10 | 50 | $70 | $1.40 |
| 10x10 | 100 | $110 | $1.10 |
| 10x15 | 150 | $150 | $1.00 |
| 10x20 | 200 | $190 | $0.95 |
| 10x30 | 300 | $270 | $0.90 |
The math: $45 / 25 = $1.80; $70 / 50 = $1.40; $110 / 100 = $1.10; $150 / 150 = $1.00; $190 / 200 = $0.95; $270 / 300 = $0.90.
Check the ladder for gaps
- Each step up should cost something. If a 10x15 is only $5 more than a 10x10, renters will always take the larger one and you lose rent. Here, the step is $150 - $110 = $40.
- The step from a 5x10 to a 10x10 should not be too small. Here it is $110 - $70 = $40 for 50 more square feet.
- A big jump leaves a hole. A tenant who needs 125 square feet has no good choice.
What to do with your own market
Prices depend on your town. Do this:
- Call or look up every nearby facility and write down their rents by size. The SBA advises studying competitors' strengths, weaknesses and pricing as part of competitive analysis.
- Record which sizes they say are sold out. Scarce sizes can bear higher rents.
- Compare their rent per square foot to yours.
- Read self storage pricing strategy.
Do not copy a competitor blindly. They may have discounts, older buildings or a different location.
Build a unit mix
Say you are planning 100 units on 12,500 net rentable square feet. Using the ladder above:
| Size | Units | Sq ft each | Total sq ft | Rent each | Monthly rent |
|---|---|---|---|---|---|
| 5x10 | 20 | 50 | 1,000 | $70 | $1,400 |
| 10x10 | 40 | 100 | 4,000 | $110 | $4,400 |
| 10x15 | 20 | 150 | 3,000 | $150 | $3,000 |
| 10x20 | 15 | 200 | 3,000 | $190 | $2,850 |
| 10x30 | 5 | 300 | 1,500 | $270 | $1,350 |
| Total | 100 | 12,500 | $13,000 |
Check: 1,000 + 4,000 + 3,000 + 3,000 + 1,500 = 12,500 sq ft. $1,400 + $4,400 + $3,000 + $2,850 + $1,350 = $13,000. Rent per sq ft at full occupancy: $13,000 / 12,500 = $1.04.
Now test another mix. Replace the five 10x30 units with ten 10x15 units? That changes the total area, so compare per square foot, not per unit. The unit mix calculator does this for you. For a new build, see how to start a self storage business.
Two 5x10s or one 10x10?
Two 5x10 units bring $70 x 2 = $140. One 10x10 brings $110. Smaller units earn more per square foot, so owners often divide big units where demand supports it. The costs: extra walls, doors, locks and more tenants to manage. Compare the extra rent against the work and construction cost.
Unit type matters as much as size
| Type | What it is | Effect on price |
|---|---|---|
| Interior | Inside a building, hallway access | Often priced higher for protection from weather |
| Drive-up | Door opens outdoors | Easy loading |
| Climate controlled | Temperature managed | Usually priced above standard |
| Outdoor | Parking space for vehicles | Priced differently |
See climate controlled storage guide, and the glossary entries on drive-up and interior unit.
Help renters pick the right size
Many renters rent too large or too small. Put a short guide on your website:
- A picture or description for each size.
- A line like "Fits the contents of a 1-bedroom apartment" as a rough guide, not a promise.
- A suggestion to measure the biggest item.
- A way to call or chat before they rent.
If renters can rent online, show each size with its rate and availability. Your facility website and online rentals should do this for you.
Track the results
After a few months, check:
- Which sizes fill first, and how long vacant units sit.
- Rent per square foot by size.
- Rate gap between new and existing renters.
Adjust one size at a time. See KPIs to track. The facility map shows what is vacant at a glance.
Mistakes
- Setting rents only by guesswork, with no ladder.
- A tiny gap between two sizes.
- Building only large units.
- Ignoring climate, drive-up and interior differences.
- Changing everything at once so you cannot tell what worked.
How renters pick a size
Most people think in terms of rooms, not square feet. Give them a plain comparison:
- A closet or a few boxes: 5x5.
- A dorm room or a small bedroom: 5x10.
- A one-bedroom apartment: 10x10.
- A two or three-bedroom home: 10x15 or 10x20.
- A whole house or business stock: 10x30 or more.
These are rough guides. The best help you can give is a short line on your website, "measure your largest item and add a little room to walk in," and an offer to answer questions by phone.
When to change your mix
Look for signs after at least a few months of data:
| Sign | Possible action |
|---|---|
| One size is always full with a waitlist | Raise that rent a little, or build or convert more |
| One size sits vacant for months | Cut its price, run a special, or split or convert it |
| Renters pick the next size up because the price gap is tiny | Widen the gap |
| Many callers ask for something you do not have | Consider adding it, for example outdoor parking |
Change one thing at a time and give it a full quarter before you judge it. The unit mix calculator helps you test a change before you pay for walls and doors.