How do I calculate square feet?

Answer 1

Square feet is a measure of area in the obsolete Imperial measurement system. There are simple formulae for shapes such as circles, ellipses, triangles, parallelograms (including special cases), trapezia and regular polygons with 5 or mire sides. The simplicity of the formula depends on what information you have about the shape. Then there are less simple formulae for more complex shapes.

For totally irregular shapes the options are the grid method and the lamina method. The first involves copying the shape onto a grid and then estimating the area by counting the number of cells of the grid inside the outline. The lamina method requires making a replica of the shape onto a lamina of uniform density and then deriving its area by comparing the mass of the lamina with that of a 1 foot square (or related size) of the lamina.