The formula for calculating the size of an exterior angle is: \(\text{exterior angle of a polygon} = 360 \div \text{number of sides}\) Remember the interior and exterior angle add up to 180°.

The sum of exterior angles of a polygon is 360°. The formula for calculating the size of an exterior angle is: exterior angle of a polygon = 360 ÷ number of sides. Next page. Symmetry.