Perimeter Calculator

Perimeter adds the edges: 2(l + w) for rectangles, three sides for triangles, 2πr for circles. It prices fencing, baseboards, trim, and track lengths — anywhere the cost follows the outline rather than the area.

A 1×16 rectangle and a 4×4 square both cover 16 square units, but their perimeters are 34 and 16. Circles minimize perimeter for a given area — why bubbles are round and why long skinny rooms cost more baseboard per square foot.