How to use the Cylinder Volume Calculator
- Enter the radius — half the internal diameter for a tank or pipe.
- Enter the height, or the length for a horizontal pipe.
- Read the volume in cubic units.
- Read the surface area, which includes both circular ends plus the curved wall.
- Use the litre conversion when your measurements are in centimetres.
How the calculation works
A cylinder is a circle extruded along a straight axis, so its volume is simply the circular cross-sectional area multiplied by the length of the extrusion: pi r squared times h. Nothing changes if the cylinder lies horizontally — a pipe's capacity is the same bore area times its run — which makes this one formula cover tanks, columns, drums, ducts and pipework alike.
Total surface area combines the curved side with the two flat ends. Unrolling the side gives a rectangle whose width is the circumference and whose height is h, contributing 2πrh, and each end adds πr². Which parts you actually need depends on the job: an open-topped tank needs one end, a pipe's external paint needs neither, and insulation of a closed vessel needs all three.
For anything holding liquid, always work from internal dimensions. A 100 mm nominal pipe does not have a 100 mm bore, and a steel tank's wall thickness removes real capacity. Working from the outside diameter of a thick-walled vessel can overstate capacity by several percent, which becomes a substantial error over a large tank farm.
V = πr²h; S = 2πr(r + h); litres = V in cm³ ÷ 1000Source: Cavalieri's principle applied to a circular prism; standard solid geometry.
Worked example
A cylindrical rainwater tank has a 1.1 m internal radius and stands 2.0 m tall.
- Cross-sectional area: π × 1.1² = 3.801 m².
- Volume: 3.801 × 2.0 = 7.602 m³.
- In litres: 7.602 × 1000 = 7,602 L.
- Usable to 150 mm below the rim: 3.801 × 1.85 = 7.03 m³ = 7,032 L.
7,602 L nominal capacity, around 7,030 L usable once freeboard below the overflow is allowed for.
Frequently asked questions
How do I find the volume of a partly filled horizontal tank?+
It needs the circular segment area at the fill depth multiplied by the tank length — not a linear fraction of the total, since a half-depth horizontal tank is exactly half full but a quarter-depth one is not a quarter full.
Does wall thickness matter?+
For capacity, always use the internal radius. For external coating area, use the external radius.
What is the volume of a pipe run?+
Same formula, with the pipe length as h. A 50 m run of 100 mm bore holds π × 0.05² × 50 = 0.393 m³, or 393 litres.
How many litres in a cubic metre?+
Exactly 1,000. A cubic metre of fresh water also weighs about 1,000 kg.
Last reviewed August 31, 2026. We review this page whenever the underlying formula, tax year, published rate or standard changes.