What is a bolt pattern?
Every vehicle has a fixed lug or bolt pattern based on the number of lugs, or studs, on the wheel hub. The pattern is the number of lugs your wheel mounting hub has and the diameter of the circle in which they're arranged.
Measuring Your Bolt Pattern
Should you want to measure your bolt pattern, it's easy. When measuring, note the width in both inches and millimeters as some manufacturers use one over the other.
Even Lug Number: Measure from the center of one lug to the center of the opposite lug. When shopping for a wheel, you'll see a number like this: 8 x 6.5. This means you have 8 lugs with a 6.5-inch measurement. This same pattern could also be expressed as 8 x 165mm.
Odd Lug Number: Measure from the center of one lug to the outer edge of an opposite lug. An example of an odd bolt pattern measurement looks something like this: 5 x 5.5. This means you have 5 lugs with a 5.5-inch measurement.