Storage unit size calculator
This calculator estimates the storage unit size you need from the belongings you plan to store. It returns three answers — the minimum unit that fits, a recommended size and a comfortable option — with the estimated volume in cubic feet (cu ft), the fill rate for each unit, and an explanation of why that size was chosen.
- 110+ items
- 4 steps, about 2 minutes
- No sign-up, nothing stored
Step 1 of 4 — What are you storing?
How the recommendation is worked out
The calculator converts your item list into a total volume in cubic feet, then compares that total against the usable volume of each standard unit size.
Usable volume is not the advertised volume. A unit's gross volume is its floor area multiplied by an assumed 8 ft ceiling. From that we subtract two things:
- Packing inefficiency. You stack in a storage unit, unlike a truck, but not perfectly. At moderate density about 85% of gross volume becomes belongings.
- Aisle allowance. If you need to walk in and reach things, a further 15% comes off.
The three results mean different things. Minimum is the smallest unit your items physically fit into — packed to the door, no access. Recommended is the smallest unit that leaves you under 90% full and is wide enough for your largest furniture, which is where storage stops being stressful. Comfortable is one size above that, for anyone who is unsure or storing long term.
What each packing density means
| Density | Efficiency | What it looks like | Usable in a 10x10 |
|---|---|---|---|
| Loose | 70% | Nothing stacked above head height, fragile items, room to move things around. | 560 cu ft |
| Moderate | 85% | Stacked to around 7 ft with furniture placed sensibly. The default. | 680 cu ft |
| Tight | 93% | Stacked to the ceiling, uniform boxes, disassembled furniture. Needs planning. | 744 cu ft |
Choosing "tight" is a commitment, not a free upgrade: it means disassembled furniture, uniform boxes and stacking to the ceiling. If you are not sure you will do that, leave it on moderate. How to pack a storage unit covers what tight packing actually involves.
Typical results by home size
| Home size | Estimated volume | Minimum | Recommended | Fill rate |
|---|---|---|---|---|
| Studio apartment | 278 cu ft | 5x10 | 5x10 | 82% |
| 1 bedroom apartment | 445 cu ft | 5x15 | 10x10 | 65% |
| 2 bedroom apartment | 630 cu ft | 10x10 | 10x15 | 62% |
| 3 bedroom house | 1,168 cu ft | 10x20 | 10x20 | 86% |
| 4 bedroom house | 1,632 cu ft | 10x25 | 10x30 | 80% |
Presets are complete item lists, not rules of thumb. Edit them in step 3 to match your own household.
A worked example
A two-bedroom apartment loaded from the preset comes to 630 cu ft across furniture, appliances and about 41 boxes.
At moderate density a 10x10 offers 680 cu ft of usable space, so the fill rate is 93% — that is the minimum: it fits, packed to the door, with no room to walk in. The recommendation is a 10x15 at 62%, which is the smallest unit that stays under the 90% line.
Tick "I need to walk into the unit" and the 10x10's usable space drops to 578 cu ft, pushing the same load to 109% — over 100%, so the 10x10 stops being an option at all. That single toggle changing the answer is the point. Most published size charts assume you will never open the door again.
Limitations
This calculator estimates volume. It cannot know three things that matter on the day:
- Actual unit dimensions. Advertised sizes are nominal; a "10x10" is often a few inches under in each direction.
- Door and corridor clearance. A sofa that fits the unit may not fit the opening or turn the corner. Measure before you rent — see how to measure furniture.
- How you will actually pack. The gap between careless and careful loading is roughly a whole size step.
Item volumes are packed cubic feet from our our open dataset of packed volumes, the same basis professional movers use. Assumptions, error margins and the review cycle are documented on the how we estimate.
What size storage unit do I need?
If you would rather reason it out than use the tool, the method is five steps: list what goes in, convert to cubic feet, divide by 0.85, subtract 15% if you need an aisle, then check your largest item against the door. The size-choosing guide works through each one.
For quick orientation: a studio usually fits a 5x10, a two-bedroom apartment a 10x10, and a three-bedroom house a 10x15 or 10x20 depending on the garage.
Related questions
How accurate is a storage unit size calculator?
Accurate to roughly one size step when the item list is complete, which is the useful resolution for this decision. The error comes almost entirely from two places: items left off the list, and optimism about packing. Both push in the same direction, which is why the tool reports a recommended size below 90% full rather than the tightest possible fit.
What size storage unit do I need for a 2 bedroom apartment?
A 10x10 for a typical two-bedroom of about 630 cubic feet, filling roughly 93% of the usable space. Add a garage, a patio or an access aisle and a 10x15 becomes the better call.
Does the calculator account for stacking?
Yes — that is what packing density does. It assumes you stack to a realistic height rather than filling the unit to the roof. Choosing "tight" raises the assumption to 85% of gross volume, which requires disassembled furniture and uniform boxes.
Is my data saved anywhere?
Only in your own browser, so a reload does not lose your progress. Nothing is uploaded, there is no account, and we cannot see your inventory.
Can I print or save my inventory?
Yes. The result panel has a print option that produces a clean inventory list and size recommendation — useful as a record for insurance, and as something to hand to whoever is helping you load.