Area Calculator

Square, Rectangle, Circle, Triangle, Ellipse, Trapezoid, Parallelogram

Area of a Triangle

A triangle can be defined as a polygon with three sides and three angles. The sum of internal angles of a triangle is always 180 degrees and the sum of exterior angles is always 360 degrees.

There are several ways to calculate the area of a triangle. When the side lengths are used, it is the half of the multiplication of the base and the height which is perpendiculor to that base. Area = a * h / 2 . There are several types of triangles and for all of them the area calculation is the same.

A right triangle has one internal angle of 90 degrees. The opposite side of that angle is called hypotenuse which is the longest side of the triangle.

A scalene triangle has sides with all different lengths, so the internal angles.

A isosceles triangle has 2 sides equal in length, whereas an equilateral trinagle has all sides equal in length, so the internal angles.

An obtuse triangle has one angle bigger than 90 degrees and an acute triangle has all angles less than 90 degrees.

The calculator below can be used to calculate the area of a triangle. Enter the length of the base and the hight and click on the "Calculate" button.

area of a triangle Formula

Area of a triangle = a * h / 2

a = base, h = height

The base and the height of the triangle must be perpendicular to each other.

Length of base "a":
Length of height "h":

Result (Area of Triangle):
Area of a Circle

A circle can be defined as a closed shape where all points have the same distance to the center.

The area of a circle can be calculated by multiplying the radius (the distance from any point to the center) and a mathematichal constant Π (pronounced as "Pi") which is the ratio of the circumference (the distance around the circle) to the radius. It's always the same constant and equals about 3.14159 .

The diameter of a circle is the longest distance inside the circle, which means it has to go through the center. It is twice of the length of the radius.

The calculator below can be used to calculate the area of a circle. Enter either the radius or circumference (NOT Both) and click on the "Calculate" button.

area of a circle Formula

Area of a circle = Π * r 2

Π (Pi)= ratio of circle's circumference to it's diameter (3.14159)

r = radius (half of diameter)

Circumference is defined as the distance around the circle and calculated as: c = 2 * Π * r

Enter either radius OR circumference (Not Both)
Enter radius (r):
Enter circumference (c):

Result (Area of Circle):
Area of a Square

Square is a polygon with four equal sides in length and has four equal angles. Each angle is 90 degrees (or right angle). In order to calculate the area of a square, multiply the length of two sides (each side is equal in length).

The calculator below can be used to calculate the area of a square. Enter the length of one side of the square and click on the "Calculate" button.

area of a square Formula

Area of a square = a * a = a2

a = length of one side

In square, all sides are equal in length


Enter length of one side "a":

Result (Area of Square):

Area of a Rectangle

Rectangle is a polygon with opposite sides are equal in length and has four 90 degree angles(or right angle). In order to calculate the area of a rectangle, multiply the length of the opposite sides.

The calculator below can be used to calculate the area of a rectangle. Enter the length of opposite sides and click on the "Calculate" button.

area of a rectangle Formula

Area of a rectangle = a * b

a = base, b = height

In rectangle, only opposite sides are equal in length

Length of "a":
Length of "b":

Result (Area of Rectangle):
Area of an Ellipse

An ellipse is a closed curve where all points don't have the same distance to it's center. It's similar to circle but circle has the same distance from all points.

In order to calculate the area of an ellipse, multiply the mathematichal constant Π (pronounced as "Pi") with the 1/2 of the major axis (longest distance inside the ellipse) and the minor axis (shortest distance inside the ellipse which goes through the center). It is very similar to area calculation of a circle where the radius is multiplied by itself and "Pi", in ellipse since the distance is not the same, instead of the radius, major and minor axis are used for calculation.

The calculator below can be used to calculate the area of an ellipse. Enter 1/2 of major and minor axises and click on the "Calculate" button.

area of an ellipse Formula

Area of an ellipse = Π * a * b

Π (Pi) = 3.14159

a = 1/2 of the longest diameter (1/2 major axis)

b = 1/2 of the longest line which is perpendicular to a (1/2 minor axis)

Length of "a":
Length of "b":

Result (Area of Ellipse):
Area of a Parallelogram

Parallelogram is a four sided polygon where opposite sides are parallel (as can be guessed from its name), equal in length and have the same angles.

The area of a parallelogram can be calculated by multiplying the length of base with the height.

The calculator below can be used to calculate the area of a parallelogram. Enter the length of the base and the height and click on the "Calculate" button.

area of a parallelogram Formula

Area of a paralellogram = a * h

a = base

h = vertical height (not the length of a side)

Length of base "a":
Length of height "h":

Result (Area of Parallelogram):
Area of a Trapezoid

Trapezoid is a polygon with four sides and at least two of the sides are parallel to each other, other sides may or may not be parallel. The parallel sides are called the base and other sides are legs. In order to calculate the area of a trapezoid, add the parallel sides (bases) and multiply with the height and divide by 2.

The calculator below can be used to calculate the area of a trapezoid. Enter the length of parallel sides and the height, click on the "Calculate" button.

area of a trapezoid Formula

Area of a trapezoid = (a + b) * h / 2

a = bottom length, b = top length

h = vertical height (not the length of the side)

Length of "a":
Length of "b":
Length of "h":

Result (Area of Trapezoid):