Math Lessons / Grade 5 Geometry / Regular Polygon
Look for two matching patterns

What Is a Regular Polygon?

Regular Polygon is a polygon with all sides equal and all interior angles equal. A regular polygon has equal side lengths and equal angles. That combination makes the shape highly symmetric and evenly distributed around its center.

Interactive diagram

Regular Polygon Diagram

Change the number of sides and keep watching the side lengths and interior angles stay equal.
Equality repeated around the edge

The structure behind the symmetry

Regular polygons are always convex. As the number of sides grows, the shape begins to resemble a circle more and more closely, which is why regular polygons are closely tied to circle geometry and construction work.

This topic matters because one regular-polygon idea can support many later facts at once: equal central angles, equal exterior angles, repeated symmetry, and neat formula patterns built from n.

For a regular hexagon, six equal central angles share the full 360-degree turn, so each one is 60 degrees. That same center-based thinking works for a square, pentagon, or decagon. The side count changes the numbers, but the repeated structure stays easy to follow.

A hexagon can also be concave or irregular, so do not add regular angle facts automatically. The reliable first statement is simply that the closed boundary has six sides and six vertices.

A regular polygon is convex, but the definition of a hexagon does not require regularity. An uneven six-sided boundary still has six vertices and a 720-degree interior total. Count first, then add the extra information about equality or symmetry.

The regular condition must be checked in both directions: equal sides and equal angles. A polygon that has only one of those patterns may still be useful, but it is not regular under the full definition.

  • A regular polygon has equal side lengths and equal angles.
  • A regular polygon is both equilateral and equiangular.
  • Regular polygons are always convex.
  • In a regular n-gon, all exterior angles are equal and each has measure 360 divided by n.
Order you can measure

Where regular polygons help

  • Use regular polygons in symmetry, construction, and angle-formula problems.
  • Use them when a polygon's side equality and angle equality both matter.
  • Use regular examples as clean models when learning named polygons and n-gon formulas.
Regular is not just neat-looking

Checks before calling a polygon regular

  • Do not call a polygon regular if only the sides or only the angles are equal; both must match.
  • Do not confuse regular with merely convex or merely symmetric-looking.
  • Do not forget that regular-polygon formulas depend on the side count n as well as the equality conditions.

Compare regularity with side count

Worked example

Example 1: Check equal sides and angles

Regularity requires two kinds of equality, not just a tidy-looking outline.

  • Compare every side.
  • Compare every interior angle.
  • Confirm both sets match.

The polygon is regular only when its sides and angles are all congruent.

Worked example

Example 2: Separate regular from symmetric-looking

A balanced sketch may still have unequal sides or unequal angles.

  • Read the measurements.
  • Ignore visual symmetry for a moment.
  • Use the actual marks to classify the figure.

Regularity is proved by the measurements, not by appearance.

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