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Bolt Circle / PCD Calculator

Enter the pitch circle diameter, number of holes, and start angle to generate the X/Y position of every equally spaced hole and the adjacent-hole chord distance.

Part of Workshop Calc ↗
Unit system
Direction
Ready to calculate

Enter the dimensions, then calculate to see a checkable result.

Estimate only:Confirm the drawing convention, origin, tolerances, and machine setup before drilling or machining.

02 / Method & limits

Make the calculation checkable.

Coordinate formula

For hole i, θᵢ = start angle ± i × 360° / n, xᵢ = centerX + R cos(θᵢ), and yᵢ = centerY + R sin(θᵢ), where R = PCD / 2. Use + for counterclockwise and − for clockwise. Adjacent-hole chord = 2R sin(π / n).

Worked example

For six holes on a 100 mm PCD with a 0° start angle, the radius is 50 mm and the adjacent-hole chord is 50 mm. The first hole is at X 50 mm, Y 0 mm.

Assumptions and limits

  • Center X and Center Y place the bolt circle in the selected coordinate system; direction can be clockwise or counterclockwise.
  • The calculator assumes equally spaced holes on one perfect circle.
  • Machine origin, backlash, cutter compensation, tolerances, and workholding are not included.

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