Calculate area, perimeter, diagonals, inradius, and circumradius of a regular octagon from side length.
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Result
Total area of a regular octagon with side length 5.
Also in General
Geometry
The octagon calculator computes area, perimeter, diagonals, inradius, and circumradius of a regular octagon from its side length.
A regular octagon has eight equal sides and internal angles of 135 degrees. Area = 2(1 + sqrt(2)) * s^2. Perimeter = 8s.
The circumradius (centre to vertex) is s / (2 * sin(pi/8)). The inradius (centre to side midpoint) is s / (2 * tan(pi/8)).
This calculator handles regular octagons only.
Frequently asked questions
An eight-sided polygon. Stop signs are the most recognisable regular octagon in daily life.
135 degrees. The formula is (n-2) * 180 / n = (8-2) * 180 / 8 = 135.
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