Perimeter of Triangle Calculator

Calculate triangle perimeter from side lengths. Free online triangle perimeter calculator.

The Perimeter of Triangle Calculator finds the total distance around any triangle by adding its three sides. This straightforward but essential geometry tool helps with fencing, framing, border materials, and any application where you need to know the outer edge length of a triangular shape. Enter your three side lengths and get the perimeter instantly.

Common use cases

  • Fencing triangular areas
  • Picture frame materials
  • Border and trim calculations
  • Athletic track segments
  • Craft and sewing projects

How to use

  1. Enter the length of side a
  2. Enter the length of side b
  3. Enter the length of side c
  4. Click calculate for the perimeter
  5. Verify the sum of all sides

FAQ

How is triangle perimeter calculated?

Perimeter = a + b + c, simply the sum of all three side lengths.

Can any three numbers form a triangle?

No, the triangle inequality states that any side must be less than the sum of the other two sides.

What if I only know two sides?

You need additional information like an angle or the perimeter itself to find the third side.

How does perimeter relate to area?

Perimeter and area are independent—triangles with the same perimeter can have different areas.