Common equations for area: | Shape | Equation | Variables |
| Square | | is the length of the side of the square. |
Regular triangle
|
| is the length of one side of the triangle. |
| Regular hexagon | | is the length of one side of the hexagon. |
| Regular octagon | | is the length of one side of the octagon. |
| Any regular polygon | | is the apothem, or the radius of an inscribed circle in the polygon, and is the perimeter of the polygon. |
| Any regular polygon | | is the Perimeter and is the number of sides. |
| Any regular polygon (using degree measure) | | is the Perimeter and is the number of sides. |
| Rectangle | | and are the lengths of the rectangle's sides (length and width). |
| Parallelogram (in general) | | and are the length of the base and the length of the perpendicular height, respectively. |
| Rhombus | | and are the lengths of the two diagonals of the rhombus. |
| Triangle | | and are the base and altitude (measured perpendicular to the base), respectively. |
| Triangle | | and are any two sides, and is the angle between them. |
| Circle | or | is the radius and the diameter. |
| Ellipse | | and are the semi-major and semi-minor axes, respectively. |
| Trapezoid | | and are the parallel sides and the distance (height) between the parallels. |
| Total surface area of a Cylinder | | and are the radius and height, respectively. |
| Lateral surface area of a cylinder | | and are the radius and height, respectively. |
| Total surface area of a Cone | | and are the radius and slant height, respectively. |
| Lateral surface area of a cone | | and are the radius and slant height, respectively. |
| Total surface area of a Sphere | or | and are the radius and diameter, respectively. |
| Total surface area of an ellipsoid | | See the article. |
| Circular sector | | and are the radius and angle (in radians), respectively. |
| Square to circular area conversion | | is the area of the square in square units. |
| Circular to square area conversion | | is the area of the circle in circular units.
|