Litres & liters
Cylinder Volume Calculator Litres
Convert cylinder dimensions straight into litres and cubic metres, working from millimetres, centimetres or metres.
If you think in metric, the cylinder volume calculator litres is the tool you want. Measure in mm, cm or m, and read the result in litres — with every other unit one tap away.
Metric capacity is the default for aquariums, home brewing, laboratory work and most of the world's tanks. Litres are convenient because they tie straight back to length — a cube ten centimetres on each side is exactly one litre — which is why converting from your measurements is so clean.
Using the calculator
- Measure across the circular end — the diameter or radius.
- If you measured the diameter, halve it to get the radius r.
- Square the radius and multiply by π to get the base area.
- Multiply the base area by the height h: V = π r² h.
- 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 maths in one line
The volume of a cylinder is:
V = π r² hA worked example
Worked example. Take a cylinder with a diameter of 15 cm (so a radius of 7.5 cm) and a height of 30 cm. The base area is π × 7.5² = 176.71 cm², and multiplying by the height gives a volume of about 5.30 litres (5,301 cm³ · 1.40 US gallons).
| From | To | Multiply by |
|---|---|---|
| cm³ | litres | 0.001 |
| litres | m³ | 0.001 |
| in³ | US gallons | ÷ 231 |
| ft³ | US gallons | 7.4805 |
| ft³ | litres | 28.3168 |
For anything that holds liquid, measure the inside of the cylinder — the wall takes up space that the contents cannot.
Conversions use standard factors: 1 US gallon = 231 in³, 1 Imperial gallon = 4.54609 L, 1 litre = 1000 cm³.
After you have your answer
Most jobs need one or two more things once the volume lands. The common follow-ups, with the numbers you need, are below:
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.
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.
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
Common mistakes to avoid
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.
Reading and converting your result
Showing every unit at once is about speed and safety: you see the answer in litres, gallons and cubic feet side by side, so there is no chance of applying the wrong conversion factor. Change the output unit at the top to make any of them the headline figure, switch the precision to exact if you want the value in terms of pi, and use copy-result to paste a tidy summary wherever you need it.
Related things you might need
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:
The bottom line: with the radius or diameter and the height, the volume follows immediately, and the breakdown lets you hand the same number to anyone in the unit they prefer. Measure inside dimensions for anything that holds liquid, leave a little headspace at the top of a real container, and treat the geometric figure as a clean maximum rather than the final word on usable capacity.
Good to know
How many litres is one cubic metre?
Can I enter millimetres?
What is the formula for the volume of a cylinder?
V = π r² h — the area of the circular base (π r²) multiplied by the height (h). If you have the diameter instead of the radius, halve it first: r = d ÷ 2.