Bolt circle (PCD) calculator

Enter the bolt circle diameter (PCD), the number of holes and the angle of the first hole to get the X and Y coordinates of equally spaced holes. Useful for flanges, bolt patterns and CNC program coordinates.

⊕Hole positions

Bolt circle diameter (PCD) (mm)Number of holesAngle of first hole (deg, CCW from +X)Center X (mm)Center Y (mm)Direction

Hole-to-hole distance (chord)—mm

Angle between holes—deg

Hole	Angle (deg)	X	Y

X = Xc + (PCD/2) × cos θ　　Y = Yc + (PCD/2) × sin θ
θ = start angle ± 360° × (k − 1) ÷ number of holes　　chord = PCD × sin(180° ÷ number of holes)