n ≥ 3

What interior angle formula is used?

For a simple regular n-gon with n ≥ 3 sides, each interior angle is (n−2)×180° / n. The page expects an integer side count.

Does the decimal separator matter?

This calculator uses plain decimal numbers. If a result looks wrong, check whether you used a comma instead of a dot (or vice versa) where the field expects one.