Circle Calculator

Area, circumference, and diameter of a circle.

Free to use, no sign-up required. Circle Calculator is one of 198 tools built into Xenition, alongside a chat that can use them for you.

Gives the diameter, circumference and area of a circle from its radius, with a labelled diagram.

How to use Circle Calculator

Enter the Radius, the distance from the centre to the edge.
Read the Diameter, Circumference and Area.
If you only know the diameter, enter half of it as the radius.

How it works

Diameter = 2r, circumference = 2πr and area = πr², using the full precision of π and showing up to four decimal places. Area is in square units of whatever unit you used for the radius.

Example

A circle with a radius of 5 has a diameter of 10, a circumference of 31.4159 and an area of 78.5398.

Questions about Circle Calculator

How do I find the radius from the circumference?

Divide the circumference by 2π, about 6.2832. A circumference of 31.4159 gives a radius of 5.

Does doubling the radius double the area?

No, it multiplies it by four, because area depends on the radius squared. Circumference does double, since it grows in step with the radius.

Use it from chat

You do not have to open Circle Calculator to use it. Ask Xenition in plain language and it runs the right tool, then carries the answer into whatever you are working on — a document, a spreadsheet, a deck.

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