Fixtra

Bolt Circle Calculator

Get the X-Y and polar coordinates of every hole on a bolt circle from the diameter, number of holes, start angle and center — with a live plot. For CNC programming, layout and inspection.

Bolt circle

0° is to the right (+X), measured counter-clockwise.

Pattern

Hole coordinates

X = Cx + (BCD/2)·cos θ, Y = Cy + (BCD/2)·sin θ, with θ stepping by 360°/N from the start angle. Angle is measured counter-clockwise from +X.