How to use this calculator
- Enter bolt circle diameter and choose units.
- Set rotation offset to align the square as required.
- Provide hole size, bolt size, and plate dimensions.
- Shift origin to position the pattern on your drawing.
- Pick ordering, optionally include center, then export.
Results
Square side (center-to-center)
106.066 mm
Across corners (diagonal)
150.000 mm
Adjacent spacing on square
106.066 mm
Hole ⌀ / Bolt ⌀ / Clearance
12.000 / 10.000 / 2.000 mm
Minimum edge clearance on plate
40.967 mm
Origin shift (X, Y)
(0.000, 0.000) mm
Square bolt coordinates (origin applied)
| Point | X (mm) | Y (mm) |
|---|---|---|
| Bolt 1 | 53.033 | 53.033 |
| Bolt 2 | -53.033 | 53.033 |
| Bolt 3 | -53.033 | -53.033 |
| Bolt 4 | 53.033 | -53.033 |
Coordinates reference: origin at pattern center then shifted by (X0,Y0). Rotation offset rotates the square about the origin before shifting.
Formula used
For a square pattern inscribed in a circle of diameter D, the square’s diagonal equals D. Therefore square side s = D / √2. Adjacent spacing on the square equals s.
Square coordinates (centered at origin) before rotation: (±s/2, ±s/2). Applying rotation offset θ: x' = x cosθ − y sinθ, y' = x sinθ + y cosθ. Final coordinates add origin shift (x0,y0).
Edge clearance is the minimum distance from any hole edge to the nearest plate edge. Clearance fit equals hole diameter minus bolt diameter.
Example data table
| Example | BCD | Square side | Adjacent spacing | Diagonal | Units |
|---|---|---|---|---|---|
| D=100.0 | 100.0 | 70.711 | 70.711 | 100.0 | mm |
| D=114.3 | 114.3 | 80.822 | 80.822 | 114.3 | mm |
| D=127.0 | 127.0 | 89.803 | 89.803 | 127.0 | mm |
| D=6.500 | 6.500 | 4.596 | 4.596 | 6.500 | in |
Examples assume zero rotation offset and no origin shift.
Reference & Design Data
Typical bolt sizes and recommended clearances
| Bolt size | Bolt ⌀ | Hole ⌀ (snug) | Hole ⌀ (free) | Clearance (free − bolt) | Units |
|---|---|---|---|---|---|
| M6 | 6.000 | 6.200 | 6.600 | 0.600 | mm |
| M8 | 8.000 | 8.200 | 8.800 | 0.800 | mm |
| M10 | 10.000 | 10.300 | 11.000 | 1.000 | mm |
| 1/4" | 6.350 | 6.600 | 7.100 | 0.750 | mm |
| 3/8" | 9.525 | 9.900 | 10.500 | 0.975 | mm |
Common circle → square side quick lookup
| BCD | Square side (s = D/√2) | Diagonal (equals BCD) | Units |
|---|---|---|---|
| 100.000 | 70.711 | 100.000 | mm |
| 114.300 | 80.822 | 114.300 | mm |
| 127.000 | 89.803 | 127.000 | mm |
| 139.700 | 98.783 | 139.700 | mm |
| 165.100 | 116.743 | 165.100 | mm |
| 114.300 | 80.822 | 114.300 | mm |
| 127.000 | 89.803 | 127.000 | mm |
| 139.700 | 98.783 | 139.700 | mm |
| 165.100 | 116.743 | 165.100 | mm |
Orientation & numbering rules
- Counterclockwise lists vertices V1→V4 around the square in CCW order.
- Clockwise reverses the order while keeping the same start vertex.
- Rotation offset rotates the square about the origin before any origin shift.
- If “Include center” is enabled, the first row is the pilot hole at origin.
Design checks to review
- Plate edge clearance ≥ minimum shown; increase plate or reduce hole.
- Hole–bolt clearance should be positive; negative indicates interference fit.
- Verify units when exporting; enable dual-units to cross-check values.
- When welding, add extra clearance for positional tolerance and distortion.