# Area

Area is the amount of space a two dimensional (flat) surface takes up. It is useful because it is how much of a material is needed to make a hollow container. Area is the amount of surface covered by a close object or shape.

Small areas can be measured in square centimetre and large areas in square kilometre. The area of a planar figure is often written as $A$ . Areas of regular shapes such as square, rectangle, triangle and circle can be calculated through formulas. The area of an irregular shape can be approximated through grid or graph paper.

One can use different formulas to find the area of different shapes. For example:

• Area of a rectangle is the length of any two touching sides multiplied together. In other words, length times width.
• Area of a triangle is half of the base multiplied by the perpendicular height. In other words, $A={\tfrac {1}{2}}bh$ .
• Area of a circle: $A=\pi r^{2}$ The area of a flat object is related to the surface area and volume of a three-dimensional object.

The area under a curve can be found using integration, a concept from calculus.

Some units used to measure area are square foot, square mile, square metre and square kilometre.