Work out polygon interior angle instantly with clear inputs, formula shown and shareable results.
Any n-gon can be cut into n − 2 triangles from a single vertex, so its interior angles total (n − 2) × 180°. Dividing by n gives each angle of a regular polygon.
Interior angle sum
Σ = (n − 2) × 180°
Each interior angle (regular)
θ = (n − 2) × 180° / n
(6 − 2) × 180° / 6 = 120°.
They form a linear pair along the extended side, so they are supplementary.