Bolt pattern or more commonly known as P.C.D (pitch circle diameter)is the diameter of an imaginary circle formed by the centers of the wheel lugs.
Bolt patterns can be 4-, 5-, 6-, or 8-lug holes. A bolt circle of 4x100 would indicate a 4-lug pattern on a circle with a diameter of 100mm.
The diagram below shows the proper method of measuring bolt patterns of plural number lug bolts and odd number lug bolts.
Bolt pattern is one of the most important data for the wheel fitment. When you install a wheel on a car, the first thing you have to check the wheel P.C.D.. Different car has different P.C.D., a Mercedes-Benz usually is in P.C.D. 5-100 while BMW is 5-120, but this is not fixed. Mercedes G550 is an exception, it is in P.C.D. 5-130. Land rover freelander is 5-114.3, ranger rover is 5-120, evoque is 5-108 and defender is 5-165.1. So when purchasing wheels, be carefull about the bolt patterns.
