Knowing the square footage allows you to calculate what materials are needed for a project or to advertise property you want to sell. Length times width is the formula for finding area when it comes to rectangular- or square-shaped sections. It's not uncommon, however, to have a room or an outdoor section that is irregularly shaped. You also can find the square footage of these areas by following a few simple formulas.
Measure all the dimensions or sides of the area.
Draw the area on graph paper using the measurements you obtained. Make sure your drawing is to scale. For instance, a centimeter could equal a foot.
Divide the drawing into shapes. Squares and rectangles are easiest, followed by triangles and then circles.
Figure the area of each shape. For rectangles and squares, multiply width by height. For triangles, multiply the base by the height and then divide by 2. For circles, multiply the radius square by 3.14 (pi). The radius of a circle is the distance from its center point to any other point on the edge of the circle.
Add the areas of all the individual shapes to find the total square footage.