Cylinder volume from diameter and height: litres and cubic units
Convert diameter to radius first, use consistent units and distinguish internal capacity from external size.
What to calculate
The volume of a right circular cylinder is V = πr²h. If you know diameter d, use r = d ÷ 2; equivalently V = πd²h ÷ 4. Keep diameter and height in the same linear unit before multiplying. A result in cm³ can be divided by 1,000 to get litres; a result in m³ is multiplied by 1,000. For a container, use internal dimensions for usable capacity. Wall thickness and a curved bottom can make exterior dimensions misleading.
Worked example
Consider an internal diameter of 20 cm and a straight internal height of 35 cm. Radius = 10 cm, so V = π × 10² × 35 ≈ 10,996 cm³, or about 11.0 L. If the tank is filled only to 30 cm, the volume below that level is π × 10² × 30 ≈ 9,425 cm³, or about 9.42 L. Each extra centimetre of fill adds approximately π × 10² = 314 cm³ in this straight section.
Common mistake
Do not insert diameter directly for r: squaring 20 instead of 10 gives four times the volume. Likewise, 20 cm and 0.35 m cannot be used together without conversion. Nominal container volume may differ from safe fill volume because of headspace, fittings, uneven base and measurement tolerances. A graduated container or manufacturer specification is better for critical dosing.
How to use the result
Use the cylinder calculator to enter a radius and height after conversion. Compare a tapering section with the cone calculator; it does not have the same cross-section at every height. The length converter keeps centimetres and metres consistent before calculation.
Related tools and reading
If you use a vessel for a salt solution, our brine concentration guide explains why solution mass and vessel volume answer different questions.