Perimeter of a triangle

Definition: The total distance around the outside of a triangle
Try this Drag any orange dot to resize the triangle. The perimeter is calculated as you drag.

How to find the perimeter of a triangle

Like any polygon, the perimeter is the total distance around the outside, which can be found by adding together the length of each side. Or as a formula: where:
a,b and c are the lengths of each side of the triangle

In the figure above, drag any orange dot to resize the triangle. From the side lengths shown, calculate the perimeter and verify your result matches the formula at the top of the diagram.

Other triangle topics


Perimeter / Area

Triangle types

Triangle centers

Congruence and Similarity

Solving triangles

Triangle quizzes and exercises