What is perimeter?
Perimeter is the total length of the boundary around a flat shape — add up every side and that's your answer. A rectangle is twice the length plus the width; a square is four times one side; a regular polygon is the number of sides times the side length. For a circle there are no straight sides, so the "perimeter" is the circumference, 2πr.
Frequently asked questions
What's the difference between perimeter and area?
Perimeter is the distance around the edge, measured in ordinary units. Area is the space inside, measured in square units.
What is the perimeter of a circle called?
The circumference. It equals 2 × π × radius, or π × diameter.
How do I find the perimeter of a regular polygon?
Multiply the number of sides by the length of one side — they're all equal in a regular polygon.