The bolt width is a starting point
Fabric sold as 44 inches wide may not give you 44 inches of cutting space. The stated width can include both selvages, and a washed or uneven piece may offer less. Usable width is the clean span you can cut across after leaving out those edges. Measure the particular fabric you'll use, rather than assuming every bolt is the same.
Press, measure and leave out the edges
Lay the fabric flat and smooth out folds before measuring. Exclude the selvages and any torn, distorted or damaged edge. If the width varies along the length, use the narrowest usable span needed for your cuts. An irregular remnant may need to be treated as several smaller rectangles instead of one full-width piece.
A small width difference changes the count
Suppose a 44-inch piece has 2 inches on each side that you won't use. Its usable width is 40 inches. Nine 4½-inch squares would need 40½ inches, so only eight fit across. Using the full width from the label would promise one square too many on every strip.
Use the measured width in the calculator
Enter that usable width for binding, backing or square cutting. Keep it with the fabric name in your notes if you're comparing several fabrics. The calculators don't remove a second selvage allowance from this number; the width you enter should already be ready to cut.