Hasn't been 45" for a very long time (with the exception of some home decorating fabric). The same with apparel fabric that hasn't been 60" for years (exception is canvas). But, because patterns list it as 45" or 60", this is the way we refer to it. Every bolt will give the width on the end under the name of the fabric. Reminder, this measurement is from selvage to selvage so you are actually about an inch less because of selvage and any fabric writing. When I help a new customer figure cottons for a quilt, bindings or similar projects, I use 40" for the calculations. This is an easier number to play with and gives a tad of wiggle room.