Bolt Circle Calculator

Generate exact X/Y coordinates for any bolt-circle hole pattern by diameter, count, and start angle.

A bolt circle places equally spaced holes around a diameter. Each hole’s X/Y coordinate comes from the radius and its angle, which steps by 360°/n.

Formula: X = (BCD/2)·cos θ, Y = (BCD/2)·sin θ, θ = (360°/n)·i

Worked Example

  1. Six holes on a 4.000 in bolt circle (radius 2.000 in), starting at 0°.
  2. Hole 2 at 60°: X = 2·cos60° = 1.000, Y = 2·sin60° = 1.732 in.

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