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Square feet to cubic metres

Self-storage is sold by floor area and collected storage is sold by volume, which is why two quotes for the same belongings can look nothing like each other. Here is the conversion, and the assumption it quietly rests on.

Why this is not a straight conversion

Square feet measure floor. Cubic metres measure space. Going from one to the other means deciding how high you are going to stack, and that single choice changes the answer by a third or more.

A unit with a 2.4 m ceiling only holds 2.4 m³ for every square metre of floor if you fill it to the ceiling, everywhere. In practice people stack to shoulder height over much of the floor, leave an access aisle, and do not stack furniture at all. So the usable figure is lower than the geometric one, and how much lower depends on what you are storing.

Anyone quoting you a price per square foot is making this assumption on your behalf without telling you what it is. It is a fair question to ask them.

Floor area, converted

Round floor areas across the range people usually ask about.

Floor area Floor area Volume at 2.4 m Volume at 2.0 m Volume at 1.8 m Full units, at 2.4 m
10 sq ft 0.9 m² 2.2 m³ 1.9 m³ 1.7 m³ 0.5
25 sq ft 2.3 m² 5.6 m³ 4.6 m³ 4.2 m³ 1.1
50 sq ft 4.6 m² 11.1 m³ 9.3 m³ 8.4 m³ 2.3
100 sq ft 9.3 m² 22.3 m³ 18.6 m³ 16.7 m³ 4.6
200 sq ft 18.6 m² 44.6 m³ 37.2 m³ 33.4 m³ 9.2
300 sq ft 27.9 m² 66.9 m³ 55.7 m³ 50.2 m³ 13.8

That last column is the geometric equivalent at full ceiling height, in Full units of 4.85 m³ usable each, carried to one decimal so you can see the arithmetic. Real storage comes in whole units and in five sizes, so a job landing at 2.3 does not mean renting three.

Doing it yourself

Two numbers are all you need:

  • Square feet to square metres: divide by 10.764.
  • Square metres to cubic metres: multiply by the height you will actually stack to.

A 50 sq ft unit is 4.6 m² of floor. Stack it 2 m high and you have about 9.3 m³ of space, which is roughly one XL storage unit, or two Full units and a bit left over.

Comparing a unit price to a unit price fairly

Weighing a self-storage unit against collected storage means working out what each costs for the same belongings over the same months, then checking that both sides include the same things. They usually do not:

  • Getting the goods there and back. A self-storage unit does not come to your door, so a like-for-like comparison includes transport in both directions.
  • One-off fees. Registration or admin charges are not always quoted with the monthly rate.
  • Term commitment. A longer contract usually carries a lower monthly rate on both sides.
  • Climate control, insurance and access hours, which may be included in one price and extra in the other.
  • VAT, which should be stated either way.

The calculator gives you the volume and the units it takes, which is the part you need before any of this is comparable. Take that to whatever quote you are given and you can see what you are being charged for rather than guessing.

See it in units

List what you are storing and get the volume and the units it takes.

Open the calculator