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Perimeter of a Polygon Calculator

Created by Hanna Pamuła, PhD
Reviewed by Bogna Szyk and Adena Benn
Last updated: Jul 13, 2023


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 for 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. Suppose we want to calculate the perimeter of an octagon shape.

  2. Type the number of sides. We've chosen the other... option, so we need to manually enter the number of sides. 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, are you curious about how to calculate its area? Then check out our area of a regular polygon calculator.
Maybe you're interested in calculating the perimeter of a circle instead of a polygon? Then our circle perimeter calculator is what you need.

Hanna Pamuła, PhD
Number of sides
Side a
in
Perimeter
P
in
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