Bolt Circle Calculator

Enter the bolt circle diameter and number of holes to get X/Y coordinates for each hole. Hole k sits at angle a = start + k × 360°/n, with X = cx + r·cos a and Y = cy + r·sin a. Angles run counter-clockwise from the +X axis.

Bolt circle diameter Number of holes Start angle (°) Center X Y Decimals

Hole-to-hole spacing (chord): = D·sin(180°/n)

Worked example

6 holes on a 100 mm circle, start 0°: hole 1 at (50, 0), hole 2 at (25, 43.3013), hole 4 at (−50, 0); spacing 100·sin 30° = 50 mm.

Check a hole spacing or a pin-to-pin distance with a gage block stack and pins.