Area is an important concept in physics, engineering, science and everyday life. Area determines how much solar energy can be collected from a solar panel, how much grain can be grown in a plot of land, and how much paint you need to cover a wall. Calculating area can be complicated for some shapes, but they are measured in square feet, square meters or square miles because the area of a square is the most basic of all to calculate.
Find the length of the first side of your square or rectangle in linear units, and call this length X.
Find the length of a side adjacent and perpendicular to the first side, and call this length Y. If you know your shape is a square, you can just set Y equal to X.
Multiply X by Y to get the area of the rectangle in square units. So if the length of one side (X) is 6 inches, and the other side (Y) is 7 inches, then the area of the rectangle is 42 square inches.