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Circle Calculator

Your inputs

Fill any one field and the other three are solved. Turn on Sector mode below the results for arc, sector, chord and segment answers.

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Result visualization

Solve a circle from any one measurement — radius, diameter, circumference or area — with answers in terms of π as well as decimals, a labelled diagram, worked steps, and a sector mode for arc length, sector area, chord and segment.

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UNDERSTAND YOUR RESULTS

Circle Calculator guide

Solve a circle from any one measurement — radius, diameter, circumference or area — with answers in terms of π as well as decimals, a labelled diagram, worked steps, and a sector mode for arc length, sector area, chord and segment.

How to use this tool

  1. Enter Radius, Diameter, Circumference, Area.
  2. Change a value to update the results and illustration. Check any validation message before using the output.
  3. Copy the results or download CSV. Reset restores the example values.

A worked example

Radius 5 gives diameter 10, circumference 10π (about 31.4159) and area 25π (about 78.5398). Entering the area 78.5398 on its own solves the radius back to 5, and Sector mode at 90° gives an arc length of about 7.854 and a sector area of about 19.635.

What you can do with this tool

How it works

Fill any one field and the other three are solved. Turn on Sector mode below the results for arc, sector, chord and segment answers.

Frequently asked questions

How should I interpret the illustration?

It is a visual aid, not a replacement for the numeric output. Some charts compare values with different units, and those magnitudes are not directly comparable.

Can I use the result without checking the inputs?

Check units, signs, assumptions and rounding first. The tool cannot know whether the values you enter describe the real situation correctly.