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What size storage unit do I need?

Checked Oct 2026 · numbers from the live index and the SSA UK 2026 report

Size is the biggest lever on price, and most people rent a size too big. Work from a box count, not a guess.

A medium moving box takes about 0.4 sq ft of floor when stacks run about five boxes high. That gives a quick rule of thumb:

UnitMedium boxesOr aboutUK average a month
10 sq ft25A large wardrobe's worth£27.40
15 sq ft37A box room£41.10
25 sq ft62Spare room, no furniture£68.50
50 sq ft125A one-bed flat£137
100 sq ft250A three-bed house£274

Furniture changes the sums: a sofa or a mattress wants floor or wall area you cannot stack boxes against, so add 10 to 15 sq ft per large item. Our town pages draw the popular sizes to scale so you can see the floor plan before you book.

When no unit is the right size

If your whole load is under about 100 boxes for a short stay, every unit on the market is bigger than you need, and you still pay for the van and the trips. That is the gap a per-box collection service fills: BoxSpeed charges per box, collects at the door, and the smallest "unit" is one box.

Questions

What size unit do I need for 30 boxes?

About 15 sq ft if you stack medium boxes five high. At the UK average that is £41.10 a month including VAT.

What fits in a 25 sq ft storage unit?

About 60 medium boxes stacked five high, or the contents of a spare room including a few small furniture items. It is the most commonly rented size in the UK.

Is it cheaper to rent one big unit or two small ones?

Almost always one big unit: price per square foot falls as size rises. Two small units only make sense when you need to clear one early.

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