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## Circle formulas

- Radius and diameter:

r = d/2

- Area of a circle formula:

A = πr^{2} = πd^{2}/4

- Circumference of a circle:

C = 2πr = πd

Where:

A = area

C = circumference

r = radius

π = pi = 3.14159

√ = square root

## How does this circle calculator works?

Depending on what figure needs to be calculated this circle calculator requires to input only one circle variable as explained here:

- In case the radius (r) value of a circle is provided it will calculate its area (A) and circumference (C ) by using these two equations:

A = πr^{2}

C = 2πr

- If the circle area (A) is known it will determine its radius (r) and circumference (C):

r = √(A / π)

C = 2πr

- By giving the circumference (C) of a circle it will compute its area (A) and radius (r):

r = C/2π

A = πr^{2}