Sides of a Regular Polygon
The sides of a regular polygon are the line segments that make it up.
Try this Adjust the regular polygon below by dragging any orange dot, or alter the number of sides. The length of the sides will change.

The formulas below give the length of the side of regular polygon given the number of sides and either the radius or apothem.

Side length given the apothem (inradius)

If you know the apothem (distance from the center of the polygon to the midpoint of any side - see figure above) where:
a  is the length of the apothem (inradius)
n  is the number of sides
tan  is the tangent function calculated in degrees

Side length given the radius (circumradius):

If you know the radius (distance from the center to a vertex): where:
r  is the radius (circumradius)
n  is the number of sides
sin  is the sine function calculated in degrees

Irregular polygons

The sides of an irregular polygon are essentially random lengths. There is no formula to calculate their lengths. In the figure above, uncheck 'regular' to see this.
While you are here..

... I have a small favor to ask. Over the years we have used advertising to support the site so it can remain free for everyone. However, advertising revenue is falling and I have always hated the ads. So, would you go to Patreon and become a patron of the site? When we reach the goal I will remove all advertising from the site.

It only takes a minute and any amount would be greatly appreciated. Thank you for considering it!   – John Page

Become a patron of the site at

Other polygon topics


Types of polygon

Area of various polygon types

Perimeter of various polygon types

Angles associated with polygons

Named polygons