Octagon Calculator
Calculate the area and perimeter of a regular octagon from its side length.
- Perimeter
- 40
Formula: A = 2 × (1 + √2) × a²
About Octagon Calculator
Octagon Calculator is a free online calculator that gives you an instant, accurate result as you type. Calculate the area and perimeter of a regular octagon from its side length.
The calculation uses the standard formula A = 2 × (1 + √2) × a² and updates live with every change to the inputs. Everything runs client-side in your browser — fast, private, and free to use as often as you like.
Stop signs are regular octagons — the eight-sided shape was chosen so the sign is recognizable even from behind.
Frequently Asked Questions
Is Octagon Calculator free to use?
Yes. Octagon Calculator is completely free, with no sign-up, no downloads, and no usage limits. You can use it as many times as you like on any device with a web browser.
How accurate is this calculator?
The calculator applies the standard formula (A = 2 × (1 + √2) × a²) with full floating-point precision and rounds only the displayed result. For most practical purposes the results are exact.
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