Measure the cloth, not the label
Bolts say 44/45 inches. Folded, starched, or printed off-grain, you might have 41. Quiltler’s calculators default to 42 inches usable because that is the honest planning number for most quilting cotton. If you measured 40, type 40. The fabric measurement calculator converts yards, inches, and a change of width.
Why backing cares more than binding
Binding strips are cut across the WOF, so a narrower bolt means more strips (slightly more length on the bolt). Backing is panels: each panel is one WOF wide. Crossing from 42 to 108 is the difference between three queen panels and one. See how to piece quilt backing and any size backing answer, such as queen.
Strips, fat quarters, and WOF
Jelly-roll strips are cut WOF at 2 1/2 inches. A fat quarter is not WOF — it is a short, wide rectangle. Plan fat-quarter quilts on the fat quarter quilt planner and the fat quarter calculator. Strip layouts belong to the jelly roll quilt planner.
None of this replaces piece-based yardage for a pieced top. That lives in the studio and on quilt yardage from design.