Polygon Interior Angle Calculator

Enter the number of polygon sides to calculate interior-angle sum, regular angles, and diagonal count.

Number of polygon sides

Interior-angle sum = 1080°(n − 2) × 180°

135°Each regular interior angle

45°Each exterior angle

20Diagonals

How to use this Polygon Interior Angle Calculator

Calculate the sum of interior angles and each regular interior or exterior angle. Enter your values above and the result is calculated directly in your browser. No account is required.

Fast answer, clear inputs

This tool is built around one job: give the answer quickly without forcing a signup or hiding the result. Related tools are linked nearby when the next calculation or conversion is useful.