Work out polygon perimeter instantly with clear inputs, formula shown and shareable results.
For a regular polygon every side is the same length, so the perimeter is simply the number of sides times the side length. The apothem and circumradius follow from the central angle 2π/n.
Perimeter
P = n × s
Then you must add the individual side lengths; there is no shortcut. The shoelace calculator handles irregular shapes from coordinates.
Each side subtends a central angle of 2π/n, giving s = 2R·sin(π/n) and hence R = s / (2·sin(π/n)).