Regular polygon - Definition with Examples

The Complete Prek-5 Learning Program Built for Your Child
Home > Math Vocabulary > Regular polygon

What is a Regular Polygon?

A 2-dimensional enclosed figure made by joining 3 or more straight lines is called a polygon. Polygons are also known as ‘flat figures’. 

polygon and non-polygon
            Polygon                                    Not a Polygon                                Not a Polygon
       (straight sides)                               (has a curve)                              (open, not closed)
A polygon having equal sides and equal angles is a regular polygon.

Parts of a regular polygon 

A regular polygon has three parts: 

parts of a regular polygon

The interior angle is the angle formed within the enclosed surface of the polygon by joining the sides. 

Different regular polygons 

The names of the regular polygons come from the number of sides they have.  

 Name  Figure  Sides  Interior Angle
 Equilateral triangle equilateral triangle  3 equal sides  Each angle is 60°
 Square square  4 equal sides  Each angle is 90°
 Pentagon pentagon  5 equal sides  Each angle is 108°
 Hexagon hexagon  6 equal sides  Each angle is 120°
 Heptagon heptagon  7 equal sides  Each angle is 128.57°
 Octagon octagon  8 equal sides  Each angle is 135°


  Fun facts about polygon:

  • A circle is a regular 2D shape but it is not a polygon because it does not have any straight sides.
  • Each angle of a regular polygon can be calculated by the given formula:


          where n is the number of sides in the regular polygon.


Try SplashLearn for Free
Loved by 40M+ Learners
Learners across 150+ Countries
Used in 1 in 3 Schools