Fabric Shrinkage Calculator
Calculate shrinkage percentage from a test swatch, or how much extra fabric to buy to offset it.
Reviewed by the ToolNestr Editorial Team — July 2026
How shrinkage calculation works
Shrinkage percentage is the difference between a fabric's original and post-wash measurement, divided by the original measurement. A swatch that measures 10 inches before washing and 9.5 inches after has shrunk by (10 − 9.5) ÷ 10 = 5%. Once you know this rate for a specific fabric and wash method, you can work backward to figure out how much fabric to buy so that after it shrinks, the finished piece is still the size you actually want.
The buying formula divides your desired finished length by (1 minus the shrinkage rate) — if you want a 30-inch finished panel from fabric that shrinks 5%, you need to buy 30 ÷ 0.95 ≈ 31.6 inches before washing, since that extra length is exactly what the wash will remove.
This is the standard shrinkage-allowance formula used across the textile and garment industry for pre-shrink planning.
Worked example
A 10-inch test swatch measures 9.5 inches after washing and drying, and the sewist wants a 30-inch finished curtain length.
Real-world context
Quilters and garment sewists who skip pre-washing sometimes find a finished piece has shrunk noticeably at the first laundering, which is a much harder problem to fix after construction than before cutting — testing shrinkage on a swatch first, or pre-washing the full yardage, avoids discovering the problem in a completed project.
Natural-fiber fabrics bought from overseas suppliers, where finishing processes (like sanforization, which pre-shrinks fabric mechanically) may not be applied or disclosed, benefit especially from this kind of test — a shrinkage rate that seems small per swatch can translate into several inches lost on a full curtain panel or dress length.
Common misconceptions
"Shrinkage only happens the first time you wash something." Mostly, but not always. Most shrinkage occurs on the first hot wash and dry cycle, but some natural fibers continue shrinking slightly over several washes, especially if later washed hotter than the first time.
"A fabric shrinks the same amount in length and width." Often not true. Many woven fabrics shrink more along the length (warp direction) than the width (weft), so testing and buying extra in one direction only can leave the other direction short.
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Frequently asked questions
How do I test a fabric's shrinkage before cutting?
Cut a square swatch (a 10-inch or 25cm square is common), measure it precisely, wash and dry it the same way you plan to treat the finished garment, then measure it again. The percentage difference is your shrinkage rate for that fabric and care method.
Should I test both length and width?
Yes — many fabrics, especially wovens, shrink more in one direction (usually length/warp) than the other, so measuring both dimensions separately gives a more accurate buying buffer than assuming uniform shrinkage.
Do all fabrics shrink the same amount?
No. Natural fibers like cotton and linen typically shrink more (often 3-8% depending on weave and finish) than synthetic fibers like polyester, which often shrink under 1%. Pre-washed or "sanforized" fabrics are treated specifically to minimize shrinkage.
Is it better to pre-wash fabric or buy extra to compensate?
Pre-washing the fabric before cutting is generally more reliable, since it shrinks the fabric before it becomes a garment rather than after — buying extra to compensate is a fallback for fabrics that can't be safely pre-washed (like some wools or dry-clean-only fabrics).