Pentagon Calculator
Compute area, perimeter, apothem and interior angle of a regular pentagon.
Inputs
units
Area
110.1106sq units
Perimeter
40.0000units
Apothem
5.5055units
Interior Angle
108.00°
Step by step
Interior angle
(5−2)×180/5
= 108°
Apothem
a = 8 / (2 × tan(π/5))
= 5.5055
Area
A = ½ × 40 × 5.5055
= 110.1106
How it works
A regular pentagon has 5 equal sides. Each interior angle is 108°. The apothem is the distance from the center to the midpoint of a side.
Formulas
Area
A = ½ × perimeter × apothem
- P
- Perimeter (5s)
- a
- Apothem
Apothem
a = s / (2 × tan(π/n))
- s
- Side length
- n
- Number of sides (5)
Frequently Asked Questions
What is the interior angle of a regular pentagon?
Each interior angle is exactly 108°.
What is an apothem?
The apothem is the perpendicular distance from the center to any side. It is used to calculate area.