Add up the three side lengths of a triangle to get its perimeter, the total distance around the shape. The perimeter is simply a plus b plus c, so a triangle with sides 5, 6 and 7 has a perimeter of 18 units. This tool also reports the semi perimeter, which is half the perimeter and is the value used inside Heron formula for area, plus it identifies whether the triangle is scalene, isosceles or equilateral based on how many sides match. It checks the triangle inequality too, warning you when the three lengths cannot close into a real triangle. Perimeter matters when you are fencing a triangular plot, trimming a sail, or framing a gable. Enter your three sides in a consistent unit and the perimeter returns in that same linear unit. All arithmetic runs locally in your browser at full precision, and the copy button grabs the perimeter in one click.
Add the three side lengths together to get the total distance around the triangle.
The semi perimeter is half the perimeter and is a key input for Heron formula and the inscribed circle radius.
For a real triangle each side must be shorter than the sum of the other two, known as the triangle inequality.
Add up the three side lengths of a triangle to get its perimeter, the total distance around the shape. The perimeter is simply a plus b plus c, so a triangle with sides 5, 6 and 7 has a perimeter of 18 units.
Yes. Triangle Perimeter Calculator is completely free, with no sign-up and no usage limits.
Yes. Triangle Perimeter Calculator runs in any modern web browser. There is nothing to download or install.
Yes. Triangle Perimeter Calculator runs entirely on your device in your browser, so nothing you enter is uploaded to a server.