# How to find the area of a circle?

How to find the area of a circle (S)? First you need to learn what the number "pi".

The number pi (π) is a constant, equal to 3.14, expressing the ratio of the circumference (L) to the diameter (D) of a circle: π = L / D. This ratio is the same for all circles.

In addition, to calculate the area of a circle, you need to know its diameter:

Thus, it is possible to calculate the area of a circle with a diameter of 4 cm so => S = 3.14 * 42/ 4 = 12.56 cm2.

Knowing the radius (R) of the circle, the area can be calculated by the following formula:

Calculate the area of a circle, radius, for example, 3.5 cm => S = 3.14 * 3.52= 38.465 cm2.

If only the circumference (L) is known, then the following formula can be used:

based on the fact that R = L / 2π;

or

since D = L / π.

Hence the area of a circle with a circumference of, for example, 25 cm => S = 3.14 * (25/2 * 3.14)2=3,14*(25/3,14)2/ 4 = 49.75 cm2.