Circumference Calculator: Compute Dimensions of a Circle

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Below is a circumference calculator, which will compute a circle's radius, diameter, and area if you know the circumference.

Do you know a different dimension? Instead try one of the related circle dimension calculators:

Circumference Calculator

What is Circumference?

The circumference of a circle is the length of the outside boundaries of the circle.

Imagine taking a string and stretching its end around a perfect circle to touch the other end. The length of that string is the circumference.

Dimensions of a Circle

There are three heavily used dimensions that can be used to describe a circle:

  • The circumference – defined above
  • The radius – the distance from the circle's center or origin to the edge
  • The diameter – the distance from edge to edge of a circle passing through its origin or center. Conveniently, it is twice the length of a circle's radius

From any of these three measures you can find the other two, plus the area. The following equations show how the radius and diameter relate to the circumference.

The equation for circumference of a circle is:

c=\pi d

If written instead in terms of the radius, the circumference calculation is instead:

c = 2 \pi r
Dimensions of a circle: O - origin, R - radius, D - diameter, C - circumference (Wikimedia)

Area is all of the space enclosed inside the circle's boundaries. It's also inextricably linked to the other three dimensions.

It's simplest to convert circumference to radius first, then find the circle's area:

r = (c/2\pi) \\ a = \pi r^2

Using the Circumference Calculator

You can enter the circumference and also compute radius and diameter in mils, inches, feet, yards, miles, millimeters, centimeters, meters and kilometers.

Compute area measured by square mils, square inches, square feet, square yards, square miles, acres, hectares, square millimeters, square centimeters, square meters, and square kilometers.

To run the calculator, hit the 'Calculate Circle Dimensions' button when you're happy with the input.



PK started DQYDJ in 2009 to research and discuss finance and investing and help answer financial questions. He's expanded DQYDJ to build visualizations, calculators, and interactive tools.

PK lives in New Hampshire with his wife, kids, and dog.

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