How to find the perimeter of a triangle

Add all three sides, then check that your units match.

Use all three sides

For sides a, b and c, perimeter = a + b + c. A triangle with sides 5 cm, 6 cm and 7 cm has a perimeter of 18 cm.

If one side is given in meters and the others in centimeters, convert them to one unit first. A side of 0.2 m is 20 cm.

The height is the perpendicular distance used in the area formula. It is not necessarily one of the triangle’s three outside edges.