Construction Calculators

Bolt Circle Calculator

Calculate the angle between bolts and the straight-line spacing between adjacent bolts on a circular bolt pattern.

Angle between bolts —

Spacing between adjacent bolts —

About the Bolt Circle Calculator

This calculator finds the layout geometry for a circular bolt pattern — such as a flange, wheel hub or post cap — from the number of bolts and the diameter of the circle they sit on.

Formula: Angle Between Bolts = 360° ÷ Number of Bolts; Spacing Between Adjacent Bolts = Diameter × sin(180° ÷ Number of Bolts)

Use the chord spacing value to lay out bolt holes directly with a ruler or calipers, without needing a protractor. Always double-check against the actual mating part's pattern before drilling, since bolt circle diameter (BCD) conventions can vary by manufacturer.