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Circumference Calculator

This calculator works much like the circle calculator in that you can find the area, circumference and diameter of a circle.

A great feature of this calculator is that you an find the diameter from circumference, the radius from circumference, convert from circumference to area, area to circumference and so on.

Before using this calculator, it's important to understand some basics about  the circumference of a circle.

What is the circumference of a circle?

If you move along an edge of a circle, the circumference is the total length around the entire edge.  Notice how this is the same thing as perimeter with geometric figures that have many sides, as perimeter is the total distance of all sides of the polygon.

There is a distinct relationship between the radius and dimater of a circle to its circumference.

If you know the diameter (d), the circumference is C = πd.  Then since we know that the radius (r) is half the diameter. Therefore the circumference in terms of the radius is C = 2πr. You can keep the circumference in terms of π or you can calculate using the π feature on your calculator or using 3.1415926 for π.

Next, let's determine how to find the circumference using the formula above. Very simply, suppose the radius is 10 cm. Then C = 2π(10) = 62.83 cm. Quite easily done!

We can also find the area of a circle simply by using the formula A = πr^2.  For the same radius of 10 cm, the area is A = 100π  or 314.159 square cm.

So what if we have a scenario where you know the circumference but what to find the diameter or the radius? Again, this is all quite easy using the formula defined earlier.

Suppose the circumference is 100 cm.

Therefore, 100 = 2πr and r = 100/2π or approximately 15.92 cm. To find the diameter, simply double the radius to get 31.84 cm.

If you wish to avoid the manual calculations, give our circumference calculator a try for results in a mere fraction of a second.