Pentagon Formulas

1. Area of Regular Pentagon Formula

Area = \frac{1}{4} s 2 \times \sqrt 5 + 2 \sqrt 5

Area of a pentagon using side length (s).

Perimeter = 5 \times s

Perimeter is 5 times the side length (s).

a = \frac{s \times \sqrt 5 + 2 \sqrt 5}{10}

Apothem calculated using side length (s).

θ = \frac{180 \times 3}{5}

Interior angle of a regular pentagon.

Exterior Angle = \frac{360}{5}

Exterior angle is 360° divided by the number of sides.

s = \sqrt{\frac{4 \times Area}{\sqrt 5 + 2 \sqrt 5}}

Calculate side length using area.