Was ist der Lochkreis?
Der Lochkreis bezeichnet den Durchmesser des Kreises, das Zentrum der Befestigungenslöcher des Reifen verläuft.
The important measurement is the "pitch circle diameter" (PCD), usually expressed in millimeters, although inches are sometimes used. For a 4- or 6-bolt car, this measurement is merely the distance between the center of two diametrically opposite bolts. In the 4-bolt picture this would be the distance between 2 opposite holes. 
Some basic geometry is needed to find the center of a 5-bolt pattern: But basically, the PCD can be found by multiplying the center distance between any two adjacent holes by 1.701.
Or just draw an imaginary circle throught the center of all holes, now measure the diameter of this circle.