By Alina McKee | Updated Aug 30, 2022
A polygon is any flat shape with straight sides—think squares, rectangles, triangles, and parallelograms. The area of a shape represents the amount of space it occupies, measured in square units. Calculating that area is straightforward once you know the right formula for each polygon.
Confirm all four sides are equal in length. If they are, the figure is a square, not a rectangle.
Take the length of any side.
Multiply the side length by itself. For a side of 4 inches, 4 × 4 = 16. Area = side².
Measure the shorter side—this is the base.
Measure the longer side—this is the height.
Multiply base by height. The same formula works for rectangles and parallelograms: Area = base × height.
Take the length of the triangle’s base.
Determine the perpendicular distance from the base to the opposite vertex.
Multiply base by height, then divide by two: Area = (base × height) ÷ 2. This formula works for all triangles, regardless of shape.
The area of any polygon is always a positive number and can be found with a simple multiplication—and sometimes a division—depending on the shape.
