Regular polygon calculator
Works for any regular n-gon — triangle, square, pentagon, hexagon and beyond. Set the number of sides, tell the tool whether you know the side length, a radius or the area, and it derives every other property: area, perimeter, circumradius, inradius (apothem) and the interior and exterior angles.
The area is (1/4) × n × side² × cot(π/n), each interior angle is (n − 2) × 180 ÷ n degrees, and each exterior angle is 360 ÷ n degrees. All calculations stay in your browser.