area online calculator that can calculate the area of a circle from its radius or from its diameter.

The calculator has several features allowing it to make **surface calculations**.
It is thus possible to calculate the surface of a circle, also called
area of a disc through area_circle function, but also the
surface of a rectangle
, or the
surface of a square
(which is a particular rectangle).

**Calculating the area of a circle** can be done from its
radius or its diameter.

The **area of a circle** is the **area** bounded by the **circle**.
The **area of a circle** is given by the **formula** `pi*r^2` where r represents the **radius of the circle**.

Thus, **calculating the area of a circle** with radius 3 is done by typing the following formula
area_circle(`3`) , after calculation, the result `9pi` is returned.

It is also possible to make **symbolic calculation** and **calculate the area of a circle** with radius 1+x, by typing
the following formula
area_circle(`1+x`) , after calculation, the result is returned.

If d is the diameter of the circle and its radius r, then the radius of a circle is equal to half of its diameter which is expressed by the formula `r=d/2`. From this formula, it is possible to determine the area of a circle from its diameter.

The **area of a circle** can be **calculated** from its **diameter** using the
**formula** `pi*(d/2)^2`, where d is the diameter of the circle.

Thus, **calculating the area of circle** with diameter 5 is done by entering the following formula
area_circle(`5/2`) , after calculation, the result `25/4*pi` is returned.

To apply the different calculation formulas, several quizzes on the calculation of the area of the square, the rectangle, and the circle are proposed.

area_circle(radius) or area_circle(diameter/2)

area_circle(`3`) returns `9pi`

See also

- Area of a square : area_square. Area online calculator that can calculate the area of a square from the length of a side.
- Area of a circle : area_circle. Area online calculator that can calculate the area of a circle from its radius or from its diameter.
- Area of a rectangle : area_rectangle. Area online calculator that can calculate the area of a rectangle from its length and its width.
- Find equation of a straight line from two points : equation_straight_line. The equation straight line calculator allows to calculate the equation of a straight line from the coordinates of two points with step by step calculation.
- Perimeter calculator : perimeter. Online perimeter calculator that calculates rectangle perimeter, square perimeter, triangle perimeter or circle perimeter.
- Perimeter of a square : perimeter_square. The online calculator allows to calculate the perimeter of a square from the length of a side.
- Perimeter of a circle : perimeter_circle. Online calculator that calculates the perimeter of a circle from its radius.
- Perimeter of a rectangle : perimeter_rectangle. The online calculator allows to calculate the perimeter of a rectangle from its length and its width.
- Pythagorean theorem calculator : pythagorean. The calculator uses the Pythagorean theorem to verify that a triangle is right-angled or to find the length of one side of a right-angled triangle.
- Calculation of the area of a geometric figure. : area. Online area calculator which allows to calculate the area of a rectangle, square, triangle or circle.
- Volume of a cube : volume_cube. The online calculator allows to calculate the volume of a cube from the length of a side.
- Volume of a rectangular parallelepiped : volume_rectangle. The online calculator allows to calculate the volume of a rectangle from its length, its width and height.
- Volume of a sphere : volume_sphere. The online calculator allows to calculate the volume of a sphere from its radius.