There are 3 common widths for bolts of fabric: 36",44-45" and 54". Most apparel fabrics, calico, quilting fabric, etc. are 44-45" wide (and folded in half on the bolt). Most home decor fabrics are 54" (usually on rolls). 36" is less common, though you can find muslin, interfacing, and some more utilitarian fabrics in 36" widths. The width of each fabric should be labeled on the end of the bolt, along with the fiber, the care directions and how many yards were on the full bolt before cutting, the name of the fabric design & manufacturer.