// Free Engineering Tool

Bolt Circle / PCD Calculator

Calculate the X/Y coordinates of every hole on a bolt circle (pitch circle diameter) for marking out, machining or CNC. Enter PCD, number of holes and a start angle, and get each hole position, the angular spacing and the chord distance between adjacent holes — with a scaled diagram of the pattern. Exact geometry, metric or any consistent unit.

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Bolt Pattern

Pitch Circle Dia (PCD)

Number of Holes

Hole Diameter

Start Position

Start Angle

Centre X

Centre Y

Coordinates are relative to the centre (X,Y). Chord is the straight-line distance between adjacent hole centres = PCD × sin(180°/n) — useful for marking out with dividers. Angle measured counter-clockwise from the positive X-axis (3 o’clock).

Results

Angular Spacing—

Chord (adjacent holes)—

Bolt Circle Radius—

Hole Coordinates

Hole	Angle	X	Y

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Bolt Circle / PCD Calculator

Bolt Pattern

Results

Hole Coordinates Copy coordinates

Hole Coordinates