Volume of Cylinder in Litres

How to work it out

1. Measure across the circular end — the diameter or radius.
2. If you measured the diameter, halve it to get the radius r.
3. Square the radius and multiply by π to get the base area.
4. Multiply the base area by the height h: V = π r² h.
5. Convert the result into your preferred unit above.

Getting an accurate measurement

If you can only reach the top, measure the diameter across the opening and halve it. Keep every measurement in the same system, and let the tool convert between units for you.

The formula behind it

The volume of a cylinder is:

A worked example

Worked example. Take a cylinder with a diameter of 20 cm (so a radius of 10 cm) and a height of 40 cm. The base area is π × 10² = 314.16 cm², and multiplying by the height gives a volume of about 12.57 litres (12,566 cm³ · 3.32 US gallons).

Conversions use standard factors: 1 US gallon = 231 in³, 1 Imperial gallon = 4.54609 L, 1 litre = 1000 cm³.

What people work out next

Most jobs need one or two more things once the volume lands. The common follow-ups, with the numbers you need, are below:

How do I size an aquarium properly?

Measure the inside dimensions and the water height, not the glass. The litre figure guides dosing and heater sizing, but leave a few centimetres of freeboard at the top so nothing overflows.

What if my measurements are in millimetres?

Pick mm on each field. The tool converts to metres internally, so you can measure a small part in millimetres and still read a clean litre result without converting by hand.

What is that in US or Imperial gallons?

The litre result sits beside its gallon equivalents in the breakdown, so you can convert on the spot: 1000 litres is about 264 US gallons or 220 Imperial gallons.

How many millilitres or cubic centimetres is it?

One litre is exactly 1000 millilitres and 1000 cubic centimetres, so the mL and cm3 figures are just the litre value in disguise, and all three appear together in the result.

When this comes in handy

A few of the jobs it gets used for:

• Filling an aquarium to the right level
• Batch-sizing in a home brewery or kitchen
• Sizing a rainwater butt in litres
• Dosing chemicals for a metric tank

Where people go wrong

Two things trip people up: squaring the wrong number, and forgetting that the answer is cubic. If a result looks four times too big or too small, you have probably swapped radius and diameter somewhere, so it is always worth re-reading the measurement you are least sure of. It also helps to glance at the equivalent units; if the litre and gallon figures are both off by the same factor, the input is the culprit, not the maths.

Getting the number in the unit you need

One number, many units. Whatever you enter, the result lists the same volume as litres, US gallons, Imperial gallons, millilitres, cubic centimetres, cubic inches, cubic feet, cubic yards and cubic metres at the same time. You almost never have to convert by hand: read the figure in the unit your job uses and copy any of the others straight from the breakdown. If you need a shareable version, the copy-link button preserves your exact inputs so a colleague opens the page with the same calculation already filled in.

Keep going

Once you have your answer you may also want to work in gallons tank capacity volume formula. These related calculators pick up where this one leaves off:

In short: measure the width and the height, keep them in the same unit, and the tool turns them into a volume you can read in litres, gallons, cubic feet or anything else, with the working shown so you can trust it. If a result ever looks off, re-enter the measurement you are least sure of, or switch to the diameter input and let the tool halve it for you, which catches the most common error before it matters.

Good to know