Astroid Calculator

An astroid is a flat curve described by a point of a circle of radius rolling along the inner side of a circle of radius. In other words, an astroid is a hypocycloid with a module. The name of the curve in the form of “Astrois”.


Octagon Calculator

The radius of the larger circle (a)
The radius of the smaller circle (b)
Chord length (l)
Perimeter (p)
Square (S)


b = a / 4
l = 2 * a * sin( π/4 )
Р = 6 а
S = 3/8 π a2