Octagon Calculator

Use our free octagon calculator to compute the area and perimeter of a regular octagon. Enter the side length and get results instantly.

Math

Side Length (s)

Formula

A regular octagon is an eight-sided polygon with equal sides and equal angles. Its area is A = 2(1+√2) × s² and perimeter is P = 8s.

A = 2(1+√2) × s², P = 8s

Percentage: The percentage value you want to apply

Number: The original number or value

Result: The calculated result

How It Works

1Enter the side length of the regular octagon.
2Click Calculate to find the area and perimeter.
3Perimeter = 8 × side length.
4Area = 2 × (1 + √2) × side².

Examples

Regular octagon with side 5

1.Enter side = 5.
2.P = 8 × 5 = 40 units.
3.A = 2(1+√2) × 25 ≈ 120.7107 units².

Result: Area: 120.7107, Perimeter: 40.0000

Regular octagon with side 3

1.Enter side = 3.
2.P = 8 × 3 = 24 units.
3.A = 2(1+√2) × 9 ≈ 43.4558 units².

Result: Area: 43.4558, Perimeter: 24.0000

Frequently Asked Questions

A = 2(1+√2) × s², where s is the side length.

Each interior angle of a regular octagon is 135°, and the sum is 1080°.

P = 8s. Multiply the side length by 8.

Stop signs are the most common example of regular octagons in everyday life.

This calculator works for regular octagons only (equal sides and angles).

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CalculateMe Team

Last updated: 2026-07-13

Octagon Calculator

Formula

How It Works

Examples

Regular octagon with side 5

Regular octagon with side 3

Frequently Asked Questions

What is the formula for the area of a regular octagon?

How many degrees in an octagon?

What is the perimeter formula?

What are common uses for octagons?

Can I use this for irregular octagons?

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Octagon Calculator

Formula

How It Works

Examples

Regular octagon with side 5

Regular octagon with side 3

Frequently Asked Questions

What is the formula for the area of a regular octagon?

How many degrees in an octagon?

What is the perimeter formula?

What are common uses for octagons?

Can I use this for irregular octagons?

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