Bolt Circle Calculator

Your details

Forward: enter bolt circle diameter to get hole coordinates. Reverse: enter the distance between two adjacent bolts to find the bolt circle diameter.
Total number of evenly spaced holes on the bolt circle.
The diameter of the circle that passes through the centre of every hole.
mm
Angle of hole 1 measured counter-clockwise from the positive X-axis (3 o'clock position). Enter 90 for 12 o'clock.
deg
Direction in which holes are numbered from the start angle.
Individual hole size. Used only to compute the edge-to-edge gap between adjacent holes - leave at 0 to skip.
mm
X coordinate of the bolt circle centre (0 = origin).
mm
Y coordinate of the bolt circle centre (0 = origin).
mm
Bolt circle diameter
100

The diameter of the circle passing through every hole centre.

Bolt circle radius50
Angle between holes60deg
Adjacent centre-to-centre spacing50
Edge-to-edge gap between adjacent holes40
Hole 1 X50
Hole 1 Y0
Hole 2 X25
Hole 2 Y43.3013
Hole 3 X-25
Hole 3 Y43.3013
Hole coordinates summaryHole 1: X=50.0000, Y=0.0000 mm | Hole 2: X=25.0000, Y=43.3013 mm | Hole 3: X=-25.0000, Y=43.3013 mm | Hole 4: X=-50.0000, Y=0.0000 mm | Hole 5: X=-25.0000, Y=-43.3013 mm | Hole 6: X=25.0000, Y=-43.3013 mm

6-hole bolt circle: BCD = 100.0000 mm

  • The bolt circle has a radius of 50.0000 mm with 6 holes spaced 60.0000 degrees apart.
  • Adjacent hole centres are 50.0000 mm apart (chord length).
  • With a hole diameter of 10.0000 mm, the clear edge-to-edge gap between adjacent holes is 40.0000 mm.

Next stepCopy the hole coordinates from the schedule table below into your CAD drawing or CNC program. Verify the pattern on a test piece before production drilling.

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