Litres & liters
Cylinder Volume Calculator in Liters
Convert cylinder dimensions straight into litres and cubic metres, working from millimetres, centimetres or metres.
Litres are just cubic decimetres in disguise, and the cylinder volume calculator in liters handles that conversion for you. Enter the radius or diameter and the height, and the litre figure appears instantly with the cubic-metre equivalent beside it.
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.
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 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).
| 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.
Once the result is in
Most jobs need one or two more things once the volume lands. The common follow-ups, with the numbers you need, are below:
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.
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 to watch out for
The commonest slip is using the diameter where the formula wants the radius, which on its own quadruples the base area. Close behind is mixing units, such as a radius in centimetres with a height in metres. Keep every length in the same unit, or let the tool convert, and double-check whether you measured to the centre or across the whole width. When a figure looks surprising, that width measurement is almost always where the problem is hiding, so re-read it first.
Getting the number in the unit you need
Because volume units are where most errors creep in, the tool does the converting for you. Enter your measurements once and every common unit appears together, from millilitres up to cubic metres and across to US and Imperial gallons. Pick whichever the task calls for and lift the rest from the list; nothing needs a second calculation. The result also updates live as you change a measurement, so you can compare two sizes quickly without starting over.
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:
When this comes in handy
It comes in handy across quite different tasks:
- 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
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.