john65pennington Every company sets it’s own sizing standards but most are in the same ballpark. Some cut bigger and some cut tighter. For example, Banana Republic and J.Crew have a younger customer base and are more fashion driven so they tend to skew to a smaller sizing. J.C.Penney is a good mainstream resource, very middle American. They tend to be more generous in sizing.
When I try to determine sizing for my work I often look at the J,C. Penney specs. here it says 2X is 2” bigger in the chest than XXL. This doesn’t hold true for every company but it tells you that they are not always the same size. You just have to go by the inches and ignore the size label!