Method
Equation
θi = θ0 + i × 360° / Nxi = Xc + (PCD/2) cos θiChord = PCD × sin(π/N)PCD = Chord / sin(π/N)Geometry
Bolt Circle Calculator — PCD Coordinates & Chord
Enter the PCD—or a measured adjacent hole spacing—and the hole count. Dimvo returns the missing circle dimension, every X/Y coordinate, angular pitch and chord distance.
Decimal points and decimal commas are accepted.
Common hole countsholes
Origin and exact start angle
PCD is the diameter through the hole centres. Adjacent spacing is centre-to-centre, not edge distance.
Hole coordinates
Pitch circle
Ø80 mm
Adjacent spacing
40 mm
Angular pitch
60°
Centre
X0 · Y0
| Hole | Angle | X | Y |
|---|---|---|---|
| 1 | 90° | 0 mm | 40 mm |
| 2 | 150° | -34.641 mm | 20 mm |
| 3 | 210° | -34.641 mm | -20 mm |
| 4 | 270° | 0 mm | -40 mm |
| 5 | 330° | 34.641 mm | -20 mm |
| 6 | 390° | 34.641 mm | 20 mm |
Coordinate positions only. Verify units, work offset, axis direction and controller format before machining.
Quick use
How to use this calculator
- Choose whether you know the PCD or adjacent centre spacing.
- Enter the hole count and choose a simple orientation.
- Open the advanced section only when the pattern centre or first-hole angle is not standard.
Limits
Assumptions
- Equal angular spacing
- Circle centre at X0 Y0
- Angles measured counter-clockwise from +X
Provenance
Independent calculation
Generated from the displayed equation and user inputs. This page does not reproduce a standard or third-party table.
Common questions
Frequently asked questions
What is PCD?
Pitch circle diameter is the diameter of the circle through the centres of an equally spaced circular hole pattern.
How is bolt-circle chord calculated?
For N equally spaced holes, chord = PCD × sin(π/N).