To find the perimeter of a triangle, you add the lengths of all three sides together.

How to Find Perimeter of a Triangle

Basic idea

The perimeter of a triangle is the total distance around it, just like walking all the way around the edges of a park shaped like a triangle. The formula is:

P=a+b+cP=a+b+cP=a+b+c

where aaa, bbb, and ccc are the three side lengths. Example:
If a triangle has sides 3 cm, 4 cm, and 5 cm, then
P=3+4+5=12P=3+4+5=12P=3+4+5=12 cm.