With this perimeter of a polygon calculator, you'll quickly calculate - surprise, surprise - the perimeter of a regular polygon. To avoid confusion, we present the easiest option, where all you need to do is choose the polygon type and enter its side length. Other formulas that determine the perimeter of a polygon exist, too - you can use our general polygon calculator to find the polygon perimeter from other parameters.

Perimeter of a polygon formula

To calculate the perimeter of a regular polygon, simply multiply the number of sides n times the side length a:

perimeter = n * a

If you want to determine the perimeter of any polygon, sum the lengths of all its sides:

  • perimeter = Σ aᵢ

    where a₁,a₂, ..., aₙ are consecutive sides lengths

    Σ is the sum symbol (from i = 1 to n)

Or use the vertices coordinates:

  • perimeter = Σ √[(xᵢ₊₁ - xᵢ)² + (yᵢ₊₁ - yᵢ)²]

    with x(n+1) → x(1) and y(n+1) → y(1)

How to find the perimeter of a polygon?

Have a look at this easy example:

  1. Pick the polygon type. Let's suppose we want to calculate the perimeter of an octagon.

  2. Type the number of sides. We've chosen the other... option, so we need to enter the number of sides manually. It's 8.

  3. Enter the side length. Assume it's 17 in.

  4. Voilà! The perimeter of a polygon calculator shows the result. The perimeter of such an octagon is equal to 136 in.

Now that you know how to find the perimeter of a polygon, maybe you're curious how to calculate its area? Then check out our area of a polygon calculator.

Hanna Pamuła, PhD student

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Perimeter of a Regular Polygon. Calculator | Formula