Pentagon Calculator
Compute area, perimeter, apothem and interior angle of a regular pentagon.
About Pentagon Calculator
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)
Worked example
With the default values below, Pentagon Calculator returns Area of 110.1106. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Side Lengthminimum 0 units
- 8 units
Results
- Area
- 110.1106 sq units
- Perimeter
- 40.0000 units
- Apothem
- 5.5055 units
- Interior Angle
- 108.00 °
Step by step
- 1Interior angle= 108°
- 2Apothem= 5.5055
- 3Area= 110.1106
Assumptions and limits
- The result is derived only from the single input listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
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.