Work out octagon area instantly with clear inputs, formula shown and shareable results.
A regular octagon has 8 equal sides. Splitting it into 8 isosceles triangles from the centre gives A = 8s² / (4·tan(π/8)), which evaluates to 2(1+√2)·s² ≈ 4.828427·s².
Area
A = 8s² / (4·tan(π/8)) = 2(1+√2)·s² ≈ 4.828427·s²
Apothem
a = s / (2·tan(π/8))
(8 − 2) × 180° / 8 = 135°.
Yes. For an irregular octagon use the shoelace formula on its vertex coordinates instead.