Area is a measure of how much space there is on a flat surface. For example two sheets of paper have twice the area of a single sheet, because there is twice as much space to write on.
Different shapes have different ways to find the area.
For example, in a rectangle we find the area by multiplying the length times the width.
In the rectangle above, the area is 2×4 or 8. If you count the small squares you will find there are 8 of them.
(See Area of a rectangle.)
Area is measured in square units. For example in the rectangle above, if the sides are 2 and 4 meters long, then the area is 8 square meters. If the sides were 2 feet and 4 feet long the area would be 8 square feet. The most important thing to remember when calculating area is that
We talk about the rectangle above having an area of say 8 square meters, but there is a shorthand way of writing it. We write the letter for the unit with a superscript 2 after it, like this:
There are many units of area. For example, land area is measured in units like acres and hectares. The easiest way to convert from one unit to another is to use the Google search engine. A littleknown feature of it is that if you type in a conversion problem into the search box, it converts it for you if it can figure out what you mean.
For example if you type in "300 sq ft in sq m" it will tell you that 300 square feet equals 27.87 square meters.
For many shapes there are ways to calculate the area  for example the area of a circle. These are listed below with links to pages that explain each in more depth.
Square 
See Area of a square


Rectangle  
Triangle  
Triangle (SAS)  
Triangle Given 3 sides 
See Heron's formula 
See Heron's formula

Equilateral triangle 
See Equilateral area


Parallelogram  
Trapezoid 
See Trapezoid area


Rhombus  3 methods See Area of a rhombus 
See Rhombus area

Kite 
where D_{1}, D_{2} are the diagonals. 
See Area of a kite

Regular polygon  4 methods See Area of a regular polygon 

Circle 
See Area of a circle


Ellipse  
Segment of a circle  See Area of a circle segment. 

Annulus 
If you know the x,y coordinates of the vertices of a shape, there are ways to calculate the area from those coordinates. See Polygons on the coordinate plane.