Quick Answer — How Much Fabric Should You Buy?
Yardage at Width = Base Yardage (at 45in) × 45/(Fabric Width). Pattern envelope yardage charts are traditionally printed for 45" fabric, the most common apparel width. Wider fabric needs proportionally less yardage for the same pieces, since more of the pattern fits across the fabric's width in a single cut.
If your fabric has a nap or one-way directional print — velvet, corduroy, fleece, or a large-scale print that must face one direction — pattern pieces can't be flipped or rotated during layout to save fabric, which commonly adds 15-25% more yardage. This calculator applies a 20% nap allowance.
Finally, a waste buffer covers pattern matching at seams, pre-wash shrinkage, and cutting mistakes: Total to Buy = Yardage at Width (with nap) × (1 + Buffer %). 10% is a reasonable default for most projects.