A regular octagon has 8 interior angles and 8 exterior angles. Here we explain how to measure them and how to use the formula.
A regular octagon has 8 equal interior angles. Each one measures:
Each exterior angle pairs with its interior angle to make 180°:
Interior and exterior angles always add up to 180°: 135° + 45° = 180°.
For any polygon, the sum of its interior angles uses the formula (n − 2) × 180°, where n is the number of sides. For an octagon:
(8 − 2) × 180° = 6 × 180° = 1080°
Divide by 8 equal angles: 1080° ÷ 8 = 135° per angle.
Click on any element to learn more.
