Pentagon calculator

Online calculator and formulas for calculating a pentagon

Calculate pentagons online


This function calculates various parameters of a regular pentagon, a polygon with 5 vertices. Enter one of the known parameters for the calculation.


Pentagon calculator

 Input
Argument type
Value
Decimal places
 Results
Edge length a
Height h
Perimeter P
Area A
Diagonale d
Circumcir. radius ra
Incircle radius ri
Pentagon mit Ringe


Pentagon mit Ringe

Formulas for a pentagon


Circumference \(P\)

\(\displaystyle P = a · 5 \)

Area \(A\)

\(\displaystyle A =\frac{a^2}{4} · \sqrt{25+10 · \sqrt{5}} \)
\(\displaystyle ≈\frac{a^2}{4} ·6.88191 \)

Height \(h\)

\(\displaystyle h = ra+ri\)
\(\displaystyle h =\frac{a}{2} · \sqrt{5 +2· \sqrt{5}} \)
\(\displaystyle ≈\frac{a}{2} · 3.07768 \)

Calculate Diagonal \(d\)

\(\displaystyle d = \frac{a}{2} ·(1+ \sqrt{5 }) \)

Circumcircle radius \(ra\)

\(\displaystyle ra = \frac{a}{2·cos(β)}\)
\(\displaystyle ra = \frac{a}{2·cos(54)}\)
\(\displaystyle ≈\frac{a}{ 1.17557}\)

Incircle radius \(ri\)

\(\displaystyle ri= \sqrt{ra^2-a^2}\)

Edge length \(a\)

\(\displaystyle a = \frac{ h · 2}{ \sqrt{5+2·\sqrt{5}}} \)
\(\displaystyle ≈ \frac{ h · 2}{ 3.07768} \)
\(\displaystyle a = \sqrt{ \frac{ A · 4}{ \sqrt{25+10·\sqrt{5}}} } \)
\(\displaystyle ≈ \sqrt{ \frac{ A · 4}{6.88191} } \)
\(\displaystyle a = \frac{P}{5}\)
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