Area of a Regular Polygon Calculator

By Hanna Pamuła, PhD candidate
Last updated: Jun 12, 2020

This area of a regular polygon calculator can help - as you can guess - in determining the area of a regular polygon. Type the number of sides and the polygon area appears in no time. If you're wondering how to find the area of a polygon formula, keep reading and you'll find the answer! If you want to calculate the area of any 3-sided or 4-sided polygon, check out this triangle area and quadrilateral area calculator.

Area of a regular polygon formulas

The most popular, and usually the most useful formula is the one that uses the number of sides n and the side length a:

  • area = n * a² * cot(π/n) / 4

However, given other parameters, you can also find out the area:

  • area = n * a * ri / 2, having ri - incircle radius (it's also an apothem - a line segment from the center to the midpoint of one of its sides)
  • area = perimeter * ri / 2, given ri and polygon perimeter
  • area = n * (ri)² * tan(π/n), given ri
  • area = n * (rc)² * sin(2π/n) / 2, having rc - circumcircle radius

How to find the area of a polygon?

If you want to find the area of a regular polygon, simply use the formulas described above. However, if the polygon is not regular (what means it isn't equiangular and equilateral), you can:

  1. Find the area using vertices coordinates:

area = |Σ(xᵢ * yᵢ₊₁) - (yᵢ * xᵢ₊₁)| / 2

with x(n+1) → x(1) and y(n+1) → y(1)

  1. Determine the polygon area given side lengths and some diagonals, by splitting the polygon into triangles. Then find the area with given three sides (SSS) equation (it's called Heron's formula).

  2. Calculate the area of polygons using other formulas - e.g. for a scalene triangle or a quadrilateral.

Using the area of regular polygon calculator: an example

Let's assume that you want to calculate the area of a specific regular polygon, e.g. 12-sided polygon, dodecagon with 5-inch sides.

  1. Enter the number of sides of chosen polygon. Put 12 into the number of sides box.
  2. Type in the polygon side length. In our example, it's equal to 5 in.
  3. Our area of polygon calculator displays the area. It's 279.9 in².

If you want to calculate the area of a regular polygon using other parameters than the side length, check out this general regular polygon calculator.

Hanna Pamuła, PhD candidate
Number of sides
Side a
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