Octagon Radius Calculator

Calculate the radius of an octagon based on its side length or apothem

Input Parameters

Calculation Results

Calculation Formula

Octagon Radius (R) = Side Length (s)

Where:
R = Radius of the circumscribed circle
s = Side length of the octagon

Octagon Radius Calculator Usage Guide

Learn how to use the Octagon Radius Calculator and understand octagon geometry principles

How to Use This Calculator

  1. Enter the side length of your octagon in the first input field (required).
  2. Optionally, you can enter the apothem (the distance from the center to a side) if you know it.
  3. Click the "Calculate" button to compute the circumradius and inradius.
  4. The results will be displayed in the respective fields.

Understanding Octagon Geometry

An octagon is a polygon with eight sides. In this calculator:

  • Circumradius (R): The radius of the circumscribed circle that passes through all eight vertices of the octagon.
  • Inradius (r): The radius of the inscribed circle that touches all eight sides of the octagon.

Formulas Used

The calculator uses these formulas:

Circumradius: R = s / (2 × sin(π/8))

Inradius: r = s / (2 × tan(π/8))

Where s is the side length of the octagon.

Practical Applications

This calculator can be used for:

  • Designing regular octagonal structures (like stop signs, windows, or decorative elements)
  • Calculating material requirements for octagonal shapes
  • Understanding geometric properties of octagons in engineering and architecture