.
Old European area units, still in used in some private matters (e.g. land sale advertisements)
Common equations for area:
| Shape
| Equation
| Variables
|
| Square
| <math>s^2\,</math>
| <math>s</math> is the length of the side of the square.
|
| Regular hexagon
| <math>\frac{3 \sqrt{3}}{2}s^2\,</math>
| <math>s</math> is the length of one side of the hexagon.
|
| Regular octagon
| <math>2(1+\sqrt{2})s^2\,</math>
| <math>s</math> is the length of one side of the octagon.
|
| Perfect octagon
| <math>7w^2</math>
| <math>w</math> is the width of one side when all sides are equal
|
| Any regular polygon
| <math>\frac{1}{2}a p \,</math>
| <math>a</math> is the apothem, or the radius of an inscribed circle in the polygon, and <math>p</math> is the perimeter of the polygon.
|
| Rectangle
| <math>l \cdot w \,</math>
| <math>l</math> and <math>w</math> are the lengths of the rectangle's sides (length and width).
|
| Parallelogram (in general)
| <math>b \cdot h\,</math>
| <math>b</math> and <math>h</math> are the length of the base and the length of the perpendicular height, respectively.
|
| Rhombus
| <math>\frac{1}{2}ab</math>
| <math>a</math> and <math>b</math> are the lengths of the two diagonals of the rhombus.
|
| Triangle
| <math>\frac{1}{2}b \cdot h \,</math>
| <math>b</math> and <math>h</math> are the base and altitude (height), respectively.
|
| Disk* or Circle
| <math>\pi r^2 \,</math>
| <math>r</math> is the radius.
|
| Circle, Circular area
| <math>\pi r^2 \,</math>, or <math>\pi d^2/4 \,</math>
| <math>r</math> is the radius and <math>d</math> the diameter.
|
| Trapezoid
| <math>\frac{1}{2}(a+b)h \,</math>
| <math>a</math> and <math>b</math> are the parallel sides and <math>h</math> the distance (height) between the parallels.
|
| Total surface area of a Cylinder
| <math>2\pi r2+2\pi r h \,</math>
| <math>r</math> and <math>h</math> are the radius and height, respectively.
|
| Lateral surface area of a cylinder
| <math>2 \pi r h \,</math>
| <math>r</math> and <math>h</math> are the radius and height, respectively.
|
| Total surface area of a Cone
| <math>\pi r (l + r) \,</math>
| <math>r</math> and <math>l</math> are the radius and slant height, respectively.
|
| Lateral surface area of a cone
| <math>\pi r l \,</math>
| <math>r</math> and <math>l</math> are the radius and slant height, respectively.
|
| Circular sector
| <math>\frac{1}{2} r^2 \theta \,</math>
| <math>r</math> and <math>\theta</math> are the radius and angle (in radians), respectively.
|
| Square to circular area conversion
| <math>\frac{4}{\pi} A\,</math>
| <math>A</math> is the area of the square in square units.
|
| Circular to square area conversion
| <math>\frac{1}{4} C\pi\,</math>
| <math>C</math> is the area of the circle in circular units.
|
. Often such area is called
