Geometry & Shapes
Polygon Calculator
Polygon — it uses the regular-polygon area = ¼·n·s²·cot(π/n) for n sides of length s. This page runs that same calculation on your numbers, in your browser: no signup, no uploads, nothing stored.
Enter your number of sides and side length and Polygon Calculator works out the area and perimeter with standard area and perimeter formulas — fast, free and private, with no sign-up or uploads.
About this calculator
Get polygon right and the rest of the task gets easier. It uses the regular-polygon area = ¼·n·s²·cot(π/n) for n sides of length s. It matters whenever a shape has to be measured, cut, covered or compared and the geometry has to be right first. A regular hexagon with side 6: area = (3√3/2) × 6² = 93.53 . The tool above does the same computation in your browser — free, private, nothing stored.
How to use
- Enter the number of sides (3 or more).
- Enter the length of each side.
- Press Calculate to find the polygon's measurements.
- Read the area, perimeter, interior angle, and apothem.
Why use Polygon Calculator
Fast
Calculations run in your browser. No round trip to a server.
Private
Your inputs never leave your device. Nothing is uploaded.
Free
No signup, no paywall, no ads-in-results, no watermarks.
Accurate
Uses standard formulas where applicable; check critical results before relying on them.
Mobile-ready
Optimised for phones, tablets, and desktops alike.
Transparent
Honest disclaimers wherever browser limits or regional rules apply.
Common uses
Use it for school and college geometry
Use it when comparing two shapes
Use it when drafting plans and sketches
Use it for everyday area and perimeter maths
Use it when planning a garden bed
Use it for fencing and edging lengths
Technical notes
Polygon Calculator uses the regular-polygon area = ¼·n·s²·cot(π/n) for n sides of length s.
Results assume exact, idealised shapes; real-world measurement error is not included.
Results are rounded for display; the underlying calculation keeps full precision.
FAQ
Does this assume a regular polygon?
Yes. It assumes all sides and angles are equal, which is what the area and apothem formulas require.
What is the apothem?
The apothem is the distance from the centre of the polygon to the middle of any side, used to find the area.
How is the interior angle found?
Each interior angle equals (n minus 2) times 180 degrees, divided by the number of sides n.
Does the Polygon Calculator send my data to a server?
No. The Polygon Calculator runs entirely in your browser, so nothing you enter is uploaded, stored, or shared.
Worked example
A regular hexagon with side 6: area = (3√3/2) × 6² = 93.53.