BCD · hole pattern layout
Bolt Circle Calculator
Generate exact X/Y coordinates for equally spaced holes on a bolt circle — flange patterns, wheel bolt patterns and rotary table layouts. Choose hole count, circle diameter, start angle and center offset.
Bolt circle coordinates
X = R·cos θ · Y = R·sin θFormulas used
Coordinates: θᵢ = start angle + i × (360°/N); Xᵢ = Xc + R·cos θᵢ, Yᵢ = Yc + R·sin θᵢ
Chord: distance between adjacent holes = 2R·sin(180°/N) — the value to scribe when laying out by hand.
Frequently asked questions
How do I calculate bolt circle coordinates?
Divide 360° by the number of holes to get the angular step. Each hole's coordinates are X = R·cos θ and Y = R·sin θ, where θ is the start angle plus the accumulated step.
What is bolt circle diameter (BCD) for wheels?
BCD (also PCD — pitch circle diameter) is the diameter of the circle through the lug hole centers. Measure center-to-center of two adjacent holes; BCD = that chord ÷ sin(180°/N).