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Cubic metre calculator

Work out the volume of a box, a round hole or a flat area at a set depth, in cubic metres. You also get litres, cubic feet and cubic yards, and for building materials the weight in tonnes and the number of bulk bags.

Man measuring a pegged rectangular excavation for a shed base in a garden
Your result

Volume

3 m³

3,000 litres

Litres
3,000 litres
Cubic feet
105.94 ft³
Cubic yards
3.924 yd³

Add this to your project shopping list, then print it or take it to the merchant.

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How to use the cubic metre calculator

  1. Choose what you are measuring: a box, a cylinder or round hole, or an area × a depth.
  2. Type in the sizes. Each box has its own unit, so you can use metres, centimetres, millimetres, feet or inches.
  3. Pick a material if you want the weight, such as sharp sand, gravel, topsoil, concrete or water. Leave it on Nothing for the volume only.
  4. Read the volume in m³, litres, cubic feet and cubic yards. For loose materials it also shows the tonnes and the bulk bags.
  5. Tap Add to shopping list to keep the result, or Share link to send it to someone.

Why use this calculator

It is made for building and gardening, not shipping. Many cubic metre tools are for freight boxes. This one starts from a slab, a trench, a lawn or a round hole, and goes on to tonnes and bulk bags.

It turns volume into weight. Merchants sell sand, gravel and topsoil by the tonne, but you measure the job in cubic metres. Pick the material and you get both, with the density used shown in the working.

It shows the steps. Under How we worked it out you can see the volume, the litres, the cubic feet and the weight, so you can check each one.

How we worked it out

Your numbers, step by step. This updates as you change the calculator.

  1. Volume = length × width × depth = 3 m × 2 m × 0.5 m = 3 m³
  2. Litres = 3 m³ × 1,000 = 3000 litres
  3. Cubic feet = 3 m³ ÷ 0.02832 = 105.94 ft³; cubic yards = ÷ 0.7646 = 3.924 yd³

The formula

All the sums are in metres, and the answer is in cubic metres (m³).

  • Box: length × width × depth. 3 m × 2 m × 0.5 m = 3 m³.
  • Cylinder or round hole: π × radius × radius × height. The radius is half the diameter.
  • Area × depth: area in m² × depth in metres. 20 m² at 100 mm (0.1 m) = 2 m³.
  • Litres: m³ × 1,000.
  • Cubic feet: m³ ÷ 0.0283. Cubic yards: m³ ÷ 0.7646.
  • Weight: m³ × tonnes per m³ for the material you pick.
  • Bulk bags: weight ÷ 0.85 tonnes, rounded up.

For 2 m³ of topsoil: 2 × 1.5 = 3 tonnes. 3 ÷ 0.85 = 3.5, so 4 bulk bags.

What we assume

Weights are for loose material as delivered, in tonnes per m³:

Material Tonnes per m³
Sharp sand 1.7
Building sand 1.6
Gravel (10 to 20 mm) 1.7
All-in ballast 1.8
Topsoil 1.5
Concrete 2.4
Water 1.0
  • These are typical figures. Real densities vary with the supplier and with moisture. The ballast figure comes from a single supplier, so check it with yours.
  • A bulk bag holds about 850 kg. Bags sold at some shops hold 750 kg to 1 tonne, so check yours.
  • Water is 1,000 kg per m³, which is 1 tonne.
  • Concrete is about 2.4 tonnes per m³, whether wet or set. Over 1 m³ of concrete, ready-mix by lorry is usually cheaper than bags.

Tips

  • Measure small depths in millimetres. A slab 100 mm deep is 0.1 m deep. Mixing up mm and m is the easiest way to be out by 1,000 times.
  • Merchants often sell loose material by the tonne, and concrete by the m³. Use the tonnes to cubic metres converter if you only have a weight.
  • For concrete, use the concrete calculator. It adds waste, handles footings, steps and post holes, and gives bags or a ready-mix order.
  • Weights here are for loose material as delivered. Damp sand and soil weigh more, and compacted material takes up less space, so order a little extra.
  • For area and depth jobs like a lawn or a path, you can also use the topsoil calculator or the gravel calculator.

FAQs

How do I calculate cubic metres?
Multiply the length, width and depth, all in metres. A space 3 m long, 2 m wide and 0.5 m deep is 3 m³. For a round hole, use π × radius × radius × depth.
How many litres are in a cubic metre?
There are 1,000 litres in a cubic metre. So 3 m³ is 3,000 litres. A cubic metre is also 1,000,000 cm³.
How do I convert cubic feet to cubic metres?
Multiply cubic feet by 0.0283, or divide by 35.31. So 100 ft³ is about 2.83 m³. A cubic yard is 0.7646 m³.
How many cubic metres is a room?
Multiply the length, width and height. A room 4 m by 3 m with a 2.4 m ceiling is 28.8 m³. Use the box option in the calculator.
How much does a cubic metre of water, soil or concrete weigh?
Water is about 1 tonne. Concrete is about 2.4 tonnes. Topsoil is about 1.5 tonnes, and sharp sand is 1.7 tonnes. Gravel (10 to 20 mm) is about 1.7 tonnes, building sand is 1.6 and all-in ballast is 1.8.
How do I work out cubic metres of concrete, soil or gravel for a job?
Multiply the area by the depth. A 20 m² lawn bed with 100 mm of topsoil is 2 m³, which is about 3 tonnes or 4 bulk bags. For concrete, see the concrete calculator, which also adds waste.

Last reviewed: 6 November 2026 · How we calculate · Report an error