Octagon Calculator

Area and perimeter of a regular octagon.

Area 120.71

Perimeter 40

Formula: area = 2(1 + √2) × side²

Step-by-step with your numbers:

1. Values used:

2. Side length = 5

4. Area = 120.71

5. Perimeter = 40

Did we solve your problem today?

Regular eight-sided polygon measurements.

The math behind it

area = 2(1 + √2) × side² ≈ 4.828 × side². Perimeter = 8 × side.

Side 5 → area 120.7.

Stop sign?

Yes — a stop sign is a regular octagon.