How to match wheels to hubs by the number of bolts and bolt circle ?
To determine the bolt circle on wheels with an even number of bolt holes, measure center-to-center on bolt holes directly across from each other on the circumference.
Example:
8 on 6.5” would mean 8 bolt holes with 6.5’ center-to-center diameter.  On odd number bolt wheels measure any bolt hole center to the point halfway between bolt holes on the circumference.
Example:
5 on 4.5” would mean 5 bolt holes with 4.5” measure to a point halfway between the opposite bolts.