Fabric Yardage Calculator

In short This works out how much fabric to buy for a set of rectangular pieces, given the usable width of the fabric and the seam allowance you are adding. The first thing it does is the one most often got wrong: seam allowance goes on every edge, so a piece finishing at 20 by 30 inches with a half-inch allowance is CUT at 21 by 31, not 20.5 by 30.5. Allowance is added twice on each measurement because each measurement has two edges. From there it is a layout question. Pieces are laid across the usable width, as many as fit, and the rows stack down the length — so the fabric you need depends on the width you buy as much as on the pieces themselves, and a piece a little too wide to fit two across a 45-inch fabric wastes nearly half of it. Nap is the setting that catches people. Velvet, corduroy, and any one-way print look different upside down, so every piece has to run the same way up and cannot be rotated to fit better. Tick it and the estimate goes up, which is correct rather than pessimistic. Two things no layout arithmetic can predict: pre-wash anything that will ever be washed, because shrinkage after making up cannot be undone, and buy extra for a patterned fabric, because matching a print across a seam eats length that depends entirely on the size of the repeat.