generally the width of fabrics is written on the end of the bolt= along with fiber content and price- fabrics vary from
36" wide up to 44" and even 54"----it is always a good idea to check- it is not some trick- it's been that way for a long long time (since they started putting fabric on bolts)
it is (normal) for fabrics sold to quilt shops to pretty much be 40"-44" wide- but in other markets like joannes or hancocks where they sell apparel fabrics and fabrics for many other uses it is common to find other widths.