Flange Bolt Circle Calculator
Work out bolt hole spacing on a flange: angle between holes, straight chord distance, arc length and X/Y coordinates for marking or drilling.
Inputs
Results
- Angle between holes
- 45.000 °
- Chord (centre to centre)
- 76.61 mm
- Arc length between holes
- 78.62 mm
- Bolt circle radius
- 100.10 mm
- Across opposite holes
- 200.20 mm
Formula used
chord = BCD × sin(180° / n) | x = R × sin θ, y = R × cos θ
BCD is the bolt circle diameter, n the number of holes, R = BCD / 2 and θ the angle of each hole measured clockwise from the 12 o'clock position.
Hole coordinates from the flange centre (X right, Y up), in millimetres:
| Hole | Angle | X | Y |
|---|---|---|---|
| 1 | 0.00° | 0.00 | 100.10 |
| 2 | 45.00° | 70.78 | 70.78 |
| 3 | 90.00° | 100.10 | 0.00 |
| 4 | 135.00° | 70.78 | -70.78 |
| 5 | 180.00° | 0.00 | -100.10 |
| 6 | 225.00° | -70.78 | -70.78 |
| 7 | 270.00° | -100.10 | -0.00 |
| 8 | 315.00° | -70.78 | 70.78 |
Results are theoretical calculations based on the values you enter. Actual weights and quantities vary with manufacturing tolerances. Confirm requirements with our team before ordering.
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