Volume calculator: cubic meters, liters and gallons

A cubic meter calculator for real-life shapes

This volume calculator works out how much a container holds: a raised bed, a water butt, a pool, an oil tank lying on its side. Pick a shape, type the measurements and the result appears at once in cubic meters, liters, cubic decimeters, cubic centimeters, US gallons and cubic feet. Under the result you see the formula with your own numbers and a labeled diagram of the shape.

You can enter measurements in millimetres, centimetres, metres, inches or feet, so it works just as well for a hot tub sold in feet as for a tank drawn in centimetres. The "Filling time and weight of water" section then tells you how long a hose will take to fill it and how heavy the water is.

How to use it

1. Under "Shape", choose Box (cuboid), Cube, Cylinder, Horizontal tank, Cone, Frustum (bucket), Sphere or Pyramid. Under "Swimming pool", choose Rectangular pool, Round pool or Oval pool.
2. Set the "Unit of measurement". For the cylinder, cone and sphere, "Measurement you know" lets you give either the diameter or the radius.
3. Fill in the fields. Each one shows the letter used in the formula and on the diagram (L, W, h, Ø, d1, d2 and so on).
4. For several identical items, such as six planters, type 6 in "Quantity (× N)".
5. In "Flow rate (L/min)", replace the default 15 L/min with your own tap or hose flow.

"Copy the result" puts the volume, the formula and all conversions on your clipboard. Your last measurements are kept on your device.

Volume formulas

• Box: V = L × W × h. Cube: V = a³.
• Cylinder: V = π × r² × h, where r = Ø ÷ 2.
• Cone: V = π × r² × h ÷ 3. Rectangular-based pyramid: V = L × W × h ÷ 3.
• Frustum: V = π × h ÷ 3 × (R² + R × r + r²), with R and r the top and bottom radii.
• Sphere: V = 4 ÷ 3 × π × r³.
• Horizontal tank filled to depth h: the wetted area of the circle is r² × arccos((r − h) ÷ r) − (r − h) × √(2rh − h²), multiplied by the tank length L.
• Rectangular pool: V = L × W × average depth, with average depth = (d1 + d2) ÷ 2. Round pool: V = π × (Ø ÷ 2)² × d. Oval pool: V ≈ L × W × d × 0.89, a common rule of thumb, not an exact formula.

Worked example: an 8 × 4 m pool

Take a rectangular pool 8 m long and 4 m wide, 1.2 m deep at the shallow end and 2 m at the deep end. The average depth is (1.2 + 2) ÷ 2 = 1.6 m, so the volume is 8 × 4 × 1.6 = 51.2 m³. That is 51,200 liters, about 13,526 US gallons or 1,808 cubic feet, and roughly 51.2 tonnes of water. At 15 L/min (about 4 US gallons a minute), filling takes 51,200 ÷ 15 = 3,413 minutes: 56 h 53 min, close to two and a half days.

An oval above-ground pool of 6 × 3.5 m filled to 1.3 m holds about 6 × 3.5 × 1.3 × 0.89 = 24.297 m³, or roughly 6,419 US gallons. That is the figure most pool chemical labels ask for.

Conversion table

Frequently asked questions

How many liters are in a cubic meter?

Exactly 1,000. A box of 2 × 3 × 4 m holds 24 m³, which is 24,000 liters.

How do I find the volume of a cylinder?

Multiply π by the radius squared and by the height. A cylinder 1 m across and 2 m tall holds π × 0.5² × 2 = 1.5708 m³, or 1,570.8 liters.

How much is left in my horizontal tank?

Choose Horizontal tank and enter the diameter, the length and the liquid depth measured with a dipstick. A tank 2 m across and 3 m long filled to 1 m is exactly half full: 4.712 m³.

Are the gallons US or imperial?

US gallons (3.785 liters). An imperial gallon is 4.546 liters, so for UK figures divide the liters by 4.546.