Litres & liters
Cylinder Volume Liters
Convert cylinder dimensions straight into litres and cubic metres, working from millimetres, centimetres or metres.
This cylinder volume liters takes centimetre, millimetre or metre measurements and returns a clean volume in litres, along with millilitres and cubic metres. It is the quickest way to size a tank, aquarium or container in metric units.
Because a litre is just a cubic decimetre, the metric result is easy to sanity-check by eye, and the tool shows millilitres and cubic metres alongside so a small dosing job and a large storage job use the same numbers in different clothes.
How the volume is worked out
The volume of a cylinder is:
V = π r² hA worked example
Worked example. Take a cylinder with a diameter of 10 cm (so a radius of 5 cm) and a height of 25 cm. The base area is π × 5² = 78.54 cm², and multiplying by the height gives a volume of about 1.96 litres (1,963 cm³ · 0.52 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.
How the calculation works
- 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.
What people work out next
The figure above is usually the start, not the finish. These are the questions that tend to come next, answered here so you do not have to run another search:
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.
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.
Getting it right
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
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.
What to work out next
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:
Common uses
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
To sum up, the whole job is two measurements and one formula. Enter them above, pick your unit, and you have an accurate figure plus every equivalent unit beside it. Keep a copy with the copy-result button, save the shareable link if someone else needs the same numbers, and use the history panel to compare a few options without starting from scratch.