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Circle vs cylinder calculator

A flat circle has area, not volume. Here is the difference, plus the cylinder tool for when you meant a round 3-D shape.

A circle is flat: it has area, not volume. If you searched for the circle vs cylinder calculator, you probably meant a round three-dimensional shape — a cylinder or a sphere. This page explains the difference and points you to the right tool.

How to work it out

  1. Measure across the circular end — the diameter or radius.
  2. If you measured the diameter, halve it to get the radius r.
  3. Square the radius and multiply by π to get the base area.
  4. Multiply the base area by the height h: V = π r² h.
  5. Convert the result into your preferred unit above.

Worked example. Take a cylinder with a diameter of 15 cm (so a radius of 7.5 cm) and a height of 30 cm. The base area is π × 7.5² = 176.71 cm², and multiplying by the height gives a volume of about 5.30 litres (5,301 cm³ · 1.40 US gallons).

For anything that holds liquid, measure the inside of the cylinder — the wall takes up space that the contents cannot.

Every circle vs cylinder page

Each page below targets a specific question and opens with the calculator ready to go:

Frequently asked questions

Does a circle have volume?
No. A circle is two-dimensional, so it has area (π r²) but no volume. Volume belongs to solid shapes like cylinders and spheres.
I meant a round 3-D shape — what do I use?
If it has a height, it is a cylinder: use V = π r² h with the tool above. If it is a ball, that is a sphere, V = 4/3 π r³.

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