What perimeter means
Perimeter is the total distance around the edge of a shape.
Perimeter is the total distance around the outside of a 2-D shape. Imagine walking once around the edge — the total distance you walk is the perimeter.
Because perimeter is a length, it uses length units: , , , . There are no squared or cubed units in a perimeter answer.
For straight-edged shapes the method is the same: add up all the side lengths. There are shortcuts for the regular shapes you see most often.
For a rectangle of length and width :
A square is a rectangle with all four sides equal, so:
For a regular polygon with equal sides each of length :
- Perimeter = total distance around the edge.
- Units are lengths (mm, cm, m, km) — never squared.
- Rectangle: .
- Regular polygon with n sides: .