Equilateral Triangles
(KS2, Year 6)
An equilateral triangle is a triangle that has three equal angles and three sides the same length.

equilateral triangle Note: The lines through the sides of the triangle in the image above indicate they are of equal length. The arcs indicate the angles are equal.

Dictionary Definition

The Merriam-Webster dictionary defines an equilateral triangle as "a triangle in which all three sides are the same length."

Real Examples of Equilateral Triangles

Below are real examples of equilateral triangles.

equilateral triangles examples In each case
  • All 3 sides are the same length.
  • All 3 angles are the same (60°).

Properties of Equilateral Triangles

The Interior Angles of an Equilateral Triangle

Each interior angle of an equilateral triangle is 60°.

equilateral triangle interior angles

The Symmetry of Equilateral Triangles

An equilateral triangle has 3 lines of symmetry.

equilateral triangle symmetry

What's in a Name?

'Equilateral' comes from the Latin word "aequilateralis". 'aequi' comes from the word "aequalis", meaning 'equal', and 'lateralis' means 'relating to the side'. 'Equilateral' means 'equal sides'.

The Interior Angles of an Equilateral Triangle

The interior angles of any triangle add up to 180°. Since all three angles are the same in an equilateral triangle, the 180° is divided equally between each interior angle.

interior angles equilateral mini This is why each angle is 60°.

Interactive Game on the Types of Triangle

Here is an interactive game to help you learn about the types of triangle.
  • Click on a triangle so it drops into the correct "bucket."
  • In total, there are 10 triangles to clear.
  • If a triangle drops into the wrong "bucket," you will lose one of your three lives.
  • Good luck!
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This page was written by Stephen Clarke.