Online Tools and Calculators > Math > Circle Calculator

Circle Calculator

Fill in 1 variable in any field to calculate other 3 unknowns:

About Circle Calculator

The online Circle Calculator is used to calculate the area, circumference, diameter or radius of a circle. Given any one variable of a circle you can calculate the other 3 unknowns.


The following is the calculation formulas of the area, circumference and diameter of a circle whose radius is r:

The diameter of a circle

d = 2r

The circumference of a circle

C = 2πr = πd

The area of a circle

A = πr2

A = area of circle
C = circumference of circle
d = diameter of circle
r = radius of circle
π = 3.141592654

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