Circle calculator

Do not you remember the formula for calculating the area, diameter or perimeter of a circle ? Enter the circle's area, diameter, or circumference and this calculator finds the other two for you!

How to use it?

Enter the value you have beside the specified device. Touch "Solve the others" to get the results. It does not matter which length unit (milimeter, centimeter, meter, kilometer, etc.) has the value.

How to figure this out?

Area, perimeter, radius and diameter of a circle can also be easily calculated manually using some formulas and pi ( π ). Find out how in the table below.


designation Name Formula Explanation
π Pi π = O / D π is the relationship between a circle's circumference and its diameter
D Diameter D = 2 · R The diameter is the right line that goes through the circle
O Circumference D · π = O Circumference is the circle line that goes around the circle
R Radius R = D / 2 Radius is the line that runs from the center to the circle line
A Area A = π · R · R Area is the content of the circle
Tags circle area diameter circumference calculator