Area of a Circle Calculator

This calculator finds the area of a circle when the radius or diameter is known.

1. Select if you want to use the radius or diameter (default is radius).
2. For the value, you can choose a whole number, decimal or fraction.
   • You can type a fraction by typing the numerator then '/' then the denominator.
   • You can type a mixed number by typing the whole-number part, then a space then the fraction part.
   • Examples: 2 1/2 (two and one-half); 3 4/5 (three and four-fifths); 7 1/3 (seven and one-third).
3. Choose your units of measurement (default is cm)
4. Choose your desired accuracy (default is 2 decimal places)
5. Click the Find Area button
6. You will be given two answers for the area, one in terms of Pi (π) and the other answer as a decimal value.

This calculator finds the radius and diameter of the circle when the area is known.

1. Choose the area value: you can choose a whole number, decimal or fraction.
2. Choose your units of measurement (default is none)
3. Choose your desired accuracy (default is 2 decimal places)
4. Click the Find Radius button
5. You will be shown the radius and diameter of the circle as a decimal to the required accuracy.

The formula for the area of a circle is: A = πr², where r is the radius of the circle.

We hope that our calculator provides with useful step-by-step instructions for finding the area of a circle.

If you would like some more help and support try our Area of a Circle support page.

There are lots of worked examples, as well as worksheets, word problems and even an online quiz.

We have a range of area and volume calculators to help you find the area and volumes of a range of different 2d and 3d shapes.

Each calculator page comes with worked examples, formulas and practice worksheets.

We have a range of other area worksheets and support pages for a range of different 2d shapes.

Do you know the special geometric names to describe the different parts of a circle?

Well you can find all the support you need on this page, complete with some practice worksheets and an online quiz!

We have a wide range of free math calculators to help you.

Most of our calculators show you their working out so that you can see exactly what they have done to get the answer.

Our calculator hub page contains links to all of our calculators!

The Math Salamanders hope you enjoy using these free printable Math worksheets and all our other Math games and resources.

We welcome any comments about our site or worksheets on the Facebook comments box at the bottom of every page.