Fabric Shrinkage Calculator
Enter the size of your fabric or the finished size you want, plus the shrinkage percentage. The calculator gives both the post-wash size and how much larger to cut.
Tip: use URL parameters to pre-fill, e.g. ?shrinkWidth=60&shrinkLength=80&shrinkPct=3.
How the calculation works
After washing, a piece shrinks by the percentage you enter: a 60-inch width at 3% shrinkage becomes about 58.2 inches. To end at 60 inches after the same wash, cut 60 divided by 0.97, or about 61.9 inches. The calculator does this in both directions for you.
The standard advice is to add 3-5% for quilting cotton, then confirm with a wash test on a scrap piece. Shrinkage varies by fiber, weave and how you dry the fabric.
Why prewashing matters
Fabric is stretched and finished under tension, and cotton fibers relax when they get wet. The first wash releases that tension, which is why unwashed yardage can measure shorter — and narrower — than the bolt label suggests. If you plan to wash the finished quilt, prewashing the fabric first means the piecing happens after the shrinkage is already done, so blocks stay square and the quilt lies flat.
Not everyone prewashes: some quilters like the crinkled texture that un-shrunk cotton develops after the quilt is washed, and prewashing can make fabric harder to handle. Either approach is fine, but it should be a decision, not an accident — this calculator makes the prewash path predictable.
What each input means
Target width / length: the size you want the piece to be after washing. For a quilt top, use your finished quilt size; for a single block, use the block size.
Shrinkage: the expected loss as a percentage. Use 0 for prewashed fabric, 2-3 for most cotton, and up to 5 for unwashed cotton or cotton blends.
Common mistakes to avoid
- Testing with a different wash method. Water temperature, detergent and dryer heat all change shrinkage. Wash and dry your test sample exactly like the finished quilt, or the number won't transfer.
- Measuring only the length. Width shrinks too, and often at a different rate. If your pattern depends on a full 42-inch cut, test width as well.
- Adding seam allowance inside the shrinkage math. This calculator handles shrinkage only; add the 1/4-inch seams separately when cutting blocks.
- Assuming all fabrics shrink alike. Flannel and linen can shrink 5-8%, while blends shrink less. Test each fabric you plan to combine.
- Cutting first and washing later. If you skip prewashing, don't cut the project and then wash — the finished blocks will shrink unevenly and pucker around the quilting.
When to use it. Use this calculator before any fabric order if you plan to prewash, and any time a pattern says "prewash and press before cutting." It's especially important for backing and borders, where even a few percent of shrinkage on a long piece means several inches. Run it once per fabric type — the numbers are worth the five minutes. If you're buying backing, run the number twice, once for length and once for width, since both dimensions matter on a backing panel.
Common questions
How do I measure my fabric's actual shrinkage?
Cut a 10-inch square, wash and dry it the same way you will the quilt, then measure. A 10-inch square that becomes 9.7 inches means 3% shrinkage — enter that number here.
Is shrinkage the same along the length and width?
Often not exactly. Fabric usually shrinks a little more along the length than the width. The calculator applies the same percentage to both, which is fine for estimates.
Should I add seam allowance on top of the shrinkage?
Yes. This calculator only handles shrinkage. For pieces that will be sewn, add the 1/4-inch seam allowance separately, or use the quilt block calculator first and then apply shrinkage.
What about flannel and linen?
Flannel and linen can shrink more than plain cotton — often 5-8% in the first wash. Test a scrap piece before cutting your whole project.
Do I need to worry about shrinkage after the quilt is finished?
Unwashed fabric in a finished quilt will shrink unevenly around the quilting, which can cause puckering. Prewashing the fabric or choosing prewashed fabric avoids most of this.