Work out shape identifier instantly with clear inputs, formula shown and shareable results.
A polygon is named by its side count; its interior angles always sum to (sides - 2) x 180 degrees, and it has sides x (sides - 3) / 2 diagonals. Naming shapes by counting sides rather than recognising pictures is what lets a child identify an unfamiliar 11-sided figure with confidence.
Interior angle sum
sum = (sides - 2) x 180 degrees
Diagonals
diagonals = sides x (sides - 3) / 2
sum = (sides - 2) x 180 degrees. A polygon is named by its side count; its interior angles always sum to (sides - 2) x 180 degrees, and it has sides x (sides - 3) / 2 diagonals.
Naming shapes by counting sides rather than recognising pictures is what lets a child identify an unfamiliar 11-sided figure with confidence.
Enter number of sides, all sides and angles equal. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.