This calculator works out how many litres a cylinder holds, using its radius, diameter, or circumference plus its height. It suits anyone checking the real capacity of a tank, drum, pipe, tube, pot, or other cylindrical container, rather than relying on a nominal size printed on the label. Enter whichever measurement you have, radius, diameter, or circumference, along with the height or length, choose your unit (centimetres, millimetres, metres, or inches), and the calculator converts everything for you. It applies the standard formula V = pi r squared h, converting your figures to centimetres first so the result comes out accurately in litres. You get back the volume in litres as the headline figure, plus the equivalent in millilitres and cubic metres, and the radius used after conversion, so you can see how the number was reached. This is useful for sizing water tanks, checking how much a drum or pot actually holds, working out pipe capacity, or estimating fill volumes for round containers. If you are measuring a tank or drum, use the internal dimensions rather than the external ones, since wall thickness reduces the usable space. Because real containers can have rounded ends, tapered sections, or manufacturing tolerances, treat the result as a close geometric estimate of capacity rather than an exact figure for any specific product.
Enter both the radius/diameter/circumference and the height in the same unit selected above. The calculator converts everything to centimetres internally to work out litres.
A cylinder's volume is found with V = π r² h, where r is the radius (half the diameter) and h is the height or length of the cylinder. This gives the volume in cubic units matching whatever unit you measured in. To convert to litres, first get the volume into cubic centimetres, then divide by 1,000, since 1 litre is defined as exactly 1,000 cubic centimetres (1 litre = 1 cm × 1 cm × 1,000 cm, or equivalently a 10 cm cube).
Most people can measure a diameter (straight across the widest point) more easily than a radius, so this calculator lets you enter whichever you have. If you only have a tape measure and the cylinder is round (like a drum, pipe, or pot), wrap the tape around it to get the circumference, then convert to radius using r = circumference / (2 × π). All three methods give the same final volume once converted to radius.
Take a cylinder with a diameter of 30 cm and a height of 50 cm. The radius is 30 / 2 = 15 cm. The volume is π × 15² × 50 = π × 225 × 50 = π × 11,250 = approximately 35,343 cm³. Dividing by 1,000 gives approximately 35.34 litres, or 0.0353 m³.
| Object | Typical Use of This Calculator |
|---|---|
| Water tanks and drums | Checking rated capacity against actual internal dimensions |
| Plant pots and buckets | Working out soil or liquid volume for a round container |
| Pipes and tubes | Finding the internal volume for flow or fill calculations |
| Fuel and chemical drums | Confirming litres held versus the nominal drum size |
| Cylindrical concrete forms | Estimating volume before ordering concrete or fill |
For tanks and drums, always use the internal dimensions rather than the outer dimensions, since wall thickness reduces the usable capacity.
Sources: Standard geometric formula for the volume of a right circular cylinder, V = πr²h. SI unit conversions: 1 litre = 1,000 cm³ (International Bureau of Weights and Measures, SI Brochure).
This calculator assumes a right circular cylinder (uniform circular cross-section, straight sides). For tanks or drums, measure internal dimensions to get usable capacity rather than external dimensions. Results are geometric estimates; actual container capacity can vary slightly due to wall thickness, rounded ends, or manufacturing tolerances.
Find the volume in cubic centimetres using V = pi times radius squared times height, then divide by 1,000 to get litres (since 1 litre equals 1,000 cubic centimetres, and 1 cubic metre equals 1,000 litres). If you measured in millimetres, convert to centimetres first by dividing by 10, or let a calculator handle the unit conversion for you.
Yes. If you have wrapped a tape measure around a cylinder and only know the circumference, first find the radius using r = circumference / (2 x pi). Then use the usual formula, V = pi r squared h, to get the volume. This is useful for round tanks, pots, or pipes where the diameter is hard to measure directly.
A standard 44 gallon (200 litre) drum is close to 200 litres by design, with an internal diameter of around 58 cm and a height of around 88 cm. Using V = pi r squared h with r = 29 cm and h = 88 cm gives approximately 232,500 cubic centimetres, or about 232 litres, which is slightly more than the nominal 200 litre rating because real drums allow headspace and the true dimensions vary by manufacturer.
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