What it means
Fabric comes off a bolt at a fixed width and is sold by length. Buying "three yards" means three yards long — how much you actually get depends entirely on how wide the bolt is. This is why the same dress can need 4 yards or 2.75 depending on nothing but the cloth you chose.
Common widths: quilting cotton and many novelty prints at 44–45 inches. Apparel wovens, crepe, satin and lining at 56–60. Some knits and home fabrics at 60+. Velvet is often narrow at 44.
Rough conversion
Going from 44-inch to 58-inch fabric saves you roughly 30% of the length. Going the other way, multiply by about 1.4. This is a rule of thumb rather than a formula — how much you save depends on whether your pieces are wide enough to fit two across the narrower bolt, which is exactly where the saving comes from.
Where it bites
- Wide skirt panels. If a panel is 40 inches wide it fits once across a 44-inch bolt and once across a 60-inch bolt — you save nothing, and the wide fabric wasted more.
- Narrow pieces. Sleeves, bodice panels and facings nest beautifully on wide fabric.
- Very long skirts. On an expensive cloth, choosing a wider bolt can save enough to pay for the lining.
Nap, and the other thing that adds yardage
Velvet, corduroy, and any one-way print must have every piece cut facing the same direction, or the colour will read differently between panels. This removes the cutter's ability to rotate pieces to fit, and typically adds 15%. Plaids and stripes you want matched at the seams add a similar amount.
Always buy the swatch first
Colour on a screen is unreliable and drape is impossible to judge from a photograph. A swatch costs a couple of dollars and tells you both.