How cylinder volume is calculated
The volume is the area of the circular end multiplied by the height or length of the cylinder.
V = π × r² × h
- π (pi) is about 3.14159, r is the radius and h is the height or length.
- Square the radius, multiply by π to get the circular end area, then multiply by the height.
- The result is in cubic units of whatever you measured in: cubic centimetres divide by 1,000 for litres; a cubic metre is already 1,000 litres.
- Diameter is radius × 2. If you measured across the circle, enter the diameter and this calculator halves it for you.
Worked example — A tank with a 20 cm diameter (10 cm radius) and 30 cm height holds π × 10² × 30 = 9,424.78 cm³, about 9.42 litres or 2.49 US gallons.
Popular tank and pipe sizes
| Diameter | Height | Measured in | Volume | Litres | US gallons |
|---|---|---|---|---|---|
| 20 | 30 | Centimetres | 9,424.78 cm³ | 9.42 L | 2.49 gal |
| 30 | 40 | Centimetres | 28,274.33 cm³ | 28.27 L | 7.47 gal |
| 40 | 60 | Centimetres | 75,398.22 cm³ | 75.4 L | 19.92 gal |
| 60 | 80 | Centimetres | 226,194.67 cm³ | 226.19 L | 59.75 gal |
| 2 | 3 | Metres | 9.42 m³ | 9,424.78 L | 2,489.76 gal |
| 4 | 12 | Inches | 150.8 in³ | 2.47 L | 0.65 gal |
| 6 | 12 | Inches | 339.29 in³ | 5.56 L | 1.47 gal |
Swipe the table sideways to see the rest.
Diameter is measured straight across the inside of the tank or pipe. Anything not listed here goes in the calculator above.
Things to consider
- Pipes and rolls are cylinders lying down — use the pipe's length as the height.
- Measure the inside of a tank, not across the outside walls.
- If the tank is only partly filled, use the fill depth, not the full height.
- Capacity ignores wall thickness, so a real tank holds slightly less than the figure.
Frequently asked questions
How do I find the volume from the diameter?
Divide the diameter by 2 to get the radius, or enter it in the diameter field and this calculator halves it for you.
What is the formula for the volume of a cylinder?
V = π r² h — pi times the radius squared times the height.
How many litres is a cubic metre?
1,000 litres. A cubic metre is also 1,000,000 cubic centimetres.
Does this work for a tank measured in feet?
Yes. Choose feet and the volume shows in cubic feet, with litres and gallons converted.
Results are estimates for general information only, not financial, medical or professional advice.