Booking the wrong size unit is one of the most common storage mistakes — and it's almost always avoidable. Go too small and you're cramming things in awkwardly, stressing your boxes, and potentially damaging furniture. Go too large and you're paying monthly for empty floor space. Here's how to work it out before moving day.
What Size Storage Unit Do I Need? A Plain-English Guide
How unit sizes actually work
Units are measured in square feet, which gives you the floor area. What it doesn't tell you is ceiling height - most units run between 7 and 8 feet, which means vertical stacking is very much part of the usable space.
A practical way to think about it: how many rooms' worth of stuff are you storing? That tends to be a more intuitive guide than trying to visualise abstract square footage.
Unit size guide - what actually fits
Small locker or room (13-25 sq ft) - roughly the size of a large wardrobe
Good for: a handful of boxes, seasonal gear like ski equipment or Christmas decorations, a bicycle, or student belongings over the summer. Documents and archive boxes work well here too.
Not suited to: furniture, large appliances, or anything approaching a full room's worth of belongings.
Small unit (25-50 sq ft) - roughly the size of a garden shed
Fits: the contents of a small bedroom - a single bed, chest of drawers, a few boxes. Popular with small businesses storing stock, tools, or equipment.
Container equivalent: similar in floor area to a 10ft shipping container, though Think Storage units are indoor, ventilated, and purpose-built rather than metal sided.
Medium unit (50-75 sq ft) - similar to a single garage
Fits: the contents of a one-bedroom flat including furniture. A sofa, dining table, white goods, and a reasonable number of boxes will go in comfortably with sensible stacking.
Container equivalent: broadly comparable to a 20 ft shipping container in floor area – one of the most common standard sizes used in container storage.
Large unit (75-100 sq ft) - a roomy single or small double garage
Fits: contents of a two-bedroom home, or a one-bed flat with space to move around. Also suits business use - stock, display equipment, archived files.
100 sq ft - a spacious single garage
Fits: the full contents of a two-bedroom flat or house, with room to stack and access items comfortably. A practical size for anyone mid-move or storing during a renovation.
Container equivalent: just over the floor area of a standard 20ft shipping container. Unlike container storage, Think Storage units are indoors, fully ventilated, and protected from damp year-round.
115 sq ft - between a single and double garage
Fits: the contents of a two-bedroom house comfortably, with a more breathing room than the 100 sq ft unit. Good for anyone who wants reliable access without having to unstack everything to reach items at the back.
150 sq ft — roughly one and a half garages
Fits: the contents of a three-bedroom house. A significant amount of space - suitable for a full family home move, or for businesses with substantial stock or equipment requirements.
Container equivalent: comparable to a 30ft container in floor area, though that's a non-standard size in practice. More usefully, think of it as 50% more floor space than a standard 20ft container - and entirely indoors.
185 sq ft - approaching a large double garage
Fits: the full contents of a large four-bedroom house. Ample space for furniture, appliances, boxes, and items you need regular access to without reorganising the whole unit.
Container equivalent: close in floor area to a standard 40ft shipping container - the largest common container size. The difference is that a Think Storage unit at this size is climate-controlled, indoors, and accessible without a forklift or flatbed.
200 sq ft - a proper double garage
Fits: the contents of a large four-bedroom house with room to move around, or a significant business storage requirement - substantial stock levels, large equipment, trade materials.
Container equivalent: slightly larger than a standard 40ft shipping container in floor area. At this size, the advantage of an indoor, ventilated unit over open container storage becomes particularly relevant - especially for furniture, documents, or anything affected by moisture.
225 sq ft - the largest unit available at Think Storage
Fits: the full contents of a five-bedroom house, or a large-scale business storage operation. This is the right choice when you need maximum capacity combined with regular, easy access - and when you don't want to be making difficult decisions about what gets stored and what doesn't.
Container equivalent: significantly larger than a standard 40ft container. At this scale, purpose-built indoor storage is arguably a meaningfully different product from container storage - better protection, proper access, and no weather exposure.
A quick estimator
If you're still unsure, work through this mentally:
- List your large items first - sofas, beds, wardrobes, white goods. These anchor the size you need.
- Work out what can and what can not be taken apart to save space
- Count your boxes - a standard removal box is roughly 1.5 cubic feet. Thirty boxes is 45 cubic feet before you've added any furniture.
- Factor in access space - if you need to get in and out regularly, leave yourself an aisle. Don't pack every square inch.
- When in doubt, go one size up - the price difference between adjacent sizes is usually modest, and running out of space on moving day is genuinely painful.(Remember, subject to availability Think Storage always allows you to change unit size at any point in your contract).
The mistakes people make most often
Underestimating volume. Almost everyone discovers they own more than they thought once they actually start packing. It's almost universal.
Forgetting ceiling height. Stacking is your friend. Heavy, solid items at the bottom, lighter and more fragile on top.
Not leaving an access route. If there's any chance you'll need to retrieve something specific, store frequently needed items near the front. Getting to something buried at the back of a full unit is miserable.
Choosing on size alone. The shape matters too. A long, narrow unit of 50 sq. ft is considerably harder to use than a more square-shaped one of the same area. Ask when you visit or before you book to ensure you are allocated a suitable shaped unit.
Making the most of your unit
- Disassemble furniture - bed frames, wardrobes, and tables take up much less space in pieces
- Stack to the ceiling, heaviest at the bottom
- Label every box on the side as well as the top
- Wrap wooden, glass, and fabric items - moving blankets or bubble wrap
- Take a photo of the unit when loaded - saves a lot of searching later
Still not sure what size you need?
The team at Think Storage near Lisburn are happy to talk through your situation before you book. There's no obligation - and it's much easier to sort before moving day than on it.