List of formulas in elementary geometry

This is a short list of some common mathematical shapes and figures and the formulas that describe them.

Two-dimensional shapes

Shape	Area	Perimeter/Circumference	Meanings of symbols
Square	$l^{2}$	$4l$	$l$ is the length of a side
Rectangle	$lb$	$2(l+b)$	$l$ is length, $b$ is breadth
Circle	$\pi r^{2}$	$2\pi r$ or $\pi d$	where $r$ is the radius and $d$ is the diameter
Ellipse	$\pi ab$		where $a$ is the semimajor axis and $b$ is the semiminor axis
Triangle	${\frac {bh}{2}}$	$a+b+c$	$b$ is base; $h$ is height; $a,b,c$ are sides
Parallelogram	$bh$	$2(a+b)$	$b$ is base, $h$ is height, $a$ is side
Trapezoid	${\frac {a+b}{2}}h$		$a$ and $b$ are the bases

Sources:

Three-dimensional shapes

Shape	Volume	Surface area	Meanings of symbols
Cube	$l^{3}$	$6l^{2}$	$l$ is the length of a side
Rectangular Prism	$lbh$	$2(lb+lh+bh)$	$l$ = length, $h$ = height, $b$ = breadth
Sphere	${\frac {4\pi r^{3}}{3}}$	$4\pi r^{2}$	$r$ is the radius
Right circular cylinder	$\pi r^{2}h$	$2\pi r(h+r)$	$r$ is the radius and $h$ is the height

Sources:

Sphere

See also: Volume of an n-ball and n-sphere § Volume and surface area

The basic quantities describing a sphere (meaning a 2-sphere, a 2-dimensional surface inside 3-dimensional space) will be denoted by the following variables

• $r$ is the radius,
• $C=2\pi r$ is the circumference (the length of any one of its great circles),
• $S$ is the surface area,
• $V$ is the volume.

Surface area:

$${\begin{alignedat}{4}S&=4\pi r^{2}\\[0.3ex]&={\frac {1}{\pi }}C^{2}\\[0.3ex]&={\sqrt[{3}]{\pi (6V)^{2}}}\\[0.3ex]\end{alignedat}}$$

Volume:

$${\begin{alignedat}{4}V&={\frac {4}{3}}\pi r^{3}\\[0.3ex]&={\frac {1}{6\pi ^{2}}}C^{3}\\[0.3ex]&={\frac {1}{6{\sqrt {\pi }}}}S^{3/2}\\[0.3ex]\end{alignedat}}$$

Radius:

$${\begin{alignedat}{4}r&={\frac {1}{2\pi }}C\\[0.3ex]&={\sqrt {{\frac {1}{4\pi }}S}}\\[0.3ex]&={\sqrt[{3}]{{\frac {3}{4\pi }}V}}\\[0.3ex]\end{alignedat}}$$

Circumference:

$${\begin{alignedat}{4}C&=2\pi r\\[0.3ex]&={\sqrt {\pi S}}\\[0.3ex]&={\sqrt[{3}]{\pi ^{2}6V}}\\[0.3ex]\end{alignedat}}$$

See also

• Arc length – Distance along a curve
• Area#Area formulas – Size of a two-dimensional surface
• Perimeter#Formulas – Path that surrounds an area
• List of second moments of area
• List of surface-area-to-volume ratios – Surface area per unit volume
• List of surface area formulas – Measure of a two-dimensional surface
• List of trigonometric identities – Equalities that involve trigonometric functions
• List of volume formulas – Quantity of three-dimensional space