The PCD or Pitch Circle Diameter can be calculated by using some simple formulas depending on how many studs, wheel bolts or bolt holes there are.
If 'S' is the distance between two adjacent studs/bolts or holes (measured in millimetres) then the PCD would be:
4 studs/bolts or Holes = S ÷ 0.7071
5 studs/bolts or Holes = S ÷ 0.5878
6 studs/bolts or Holes = S ÷ 0.5