Inscribed polygon calculator
This tool calculates the key dimensions of any regular polygon inscribed inside a circle, supporting shapes from 3 sides (triangle) up to 50 sides. Enter either the circle's diameter or the polygon's side length and the other is calculated automatically.
For a given number of sides, the tool displays the side length, circle diameter, perimeter, and interior corner angle. For polygons with an even number of sides it also calculates the flat-to-flat distance between opposing parallel sides, while for odd-sided polygons it calculates the distance from the midpoint of a side to the opposite vertex.
A scaled diagram updates in real time to illustrate the polygon inside its circle with the key measurement highlighted.