Bolt Circle (PCD) Calculator
Distance between neighbouring holes and the X–Y coordinates of the holes on a pitch circle — flanges, wheel hubs, rotary tables — drawn to scale.
Results
Straight distance between neighbouring holes
50.000
mm
Angle between holes
60.000
°
Hole 1 — X
50.000
mm
Hole 1 — Y
0.000
mm
Hole 2 — X
25.000
mm
Hole 2 — Y
43.301
mm
What this tool does
Holes evenly spaced on a pitch circle sit at the corners of a regular polygon, so the straight distance between neighbours is PCD × sin(180°/n) — the figure to set on a pair of dividers or to check with calipers. Coordinates are measured from the centre of the circle, with angles counted anticlockwise from the X axis; each further hole is another 360°/n round. A wheel's '5×112' means five studs on a 112 mm pitch circle.
Formula
chord = PCD × sin(180° ÷ n) · hole k at (R cos(a₀ + k·360°/n), R sin(a₀ + k·360°/n))
Variables
| Symbol | Meaning | Unit |
|---|---|---|
pcd | Pitch circle diameter (PCD) | mm |
n | Number of holes | — |
a0 | Angle of the first hole | ° |
C | Straight distance between neighbouring holes | mm |
AN | Angle between holes | ° |
X1 | Hole 1 — X | mm |
Y1 | Hole 1 — Y | mm |
X2 | Hole 2 — X | mm |
Y2 | Hole 2 — Y | mm |
Worked example
- Pitch circle diameter (PCD)100 mm
- Number of holes6
- Angle of the first hole0 °
- Straight distance between neighbouring holes50.000 mm
- Angle between holes60.000 °
- Hole 1 — X50.000 mm
- Hole 1 — Y0.000 mm
- Hole 2 — X25.000 mm
- Hole 2 — Y43.301 mm
Limitations
- Mixing units is the most common source of error. Convert every input to the units shown next to each field before calculating.
- The calculation runs at full precision and only the display is rounded. If you copy an intermediate value and retype it, small differences can appear.