Square footage is the unit of measurement used to describe the entire surface area of a two-dimensional space. Determining square footage depends on the shape of the surface and involves manipulating measurements of its length and width.
Determine the shape of the target area
The formula used to determine the square footage varies for squares, triangles, circles and irregular shapes, so identify the type of shape. Sometimes the area may combine multiple shapes together, so split those areas up into more common shapes with known formulas.
Take the necessary measurements for the shape
For parallelogram shapes, such as squares and rectangles, measure both the height and width. Take the same measurements for triangles, where the width may also be referred to as the base. For circular areas, find the radius. Divide irregular shapes up into parallelograms and triangles and take the height, width or radius of the separated segments.
Plug the numbers into the proper formula
For squares and rectangles, calculate the square footage by multiplying the height and the width. For triangular areas, multiply the height and base width together and then divide that total in half. For circular areas, square the radius and multiply it by pi. Combine formulas as necessary for irregular shapes.