Fabric Shrinkage & Pre-Wash Calculator
Measure how much your fabric shrinks, then work out how much to buy and pre-wash so the finished blouse lands at the right size.
Buy this much, then pre-wash
Fabric shrinks across the width as well as the length — run this once for each direction. Pre-washing the cloth before cutting is the only sure way to keep a stitched blouse from tightening on its first wash.
Cut once, at the right size
A blouse cut from un-washed cloth can tighten noticeably the first time it’s laundered — a snug fit becomes a struggle, and a carefully placed neckline creeps upward. The fix is simple: find out how much your fabric shrinks by washing a marked swatch, then buy a little extra and pre-wash the whole piece before the scissors come out, so all the shrinking happens on the roll.
The buying figure grosses up your finished length by the shrinkage you measured, so what you cut still finishes at the size you planned. It’s the difference between a blouse that fits for years and one that never quite fits after wash day.
Frequently Asked Questions
Why does fabric shrink, and by how much?
Natural fibres are stretched during weaving and finishing; the first wash lets them relax back, so the cloth comes out smaller. Cotton commonly loses 5 to 10%, silk 3 to 8%, and linen can be more. The only reliable number is the one you measure on your own fabric, because it depends on the fibre, the weave, and how hot you wash it.
How do I measure shrinkage from a swatch?
Cut a square of the fabric, mark a known length on it (say 100cm), wash and dry it the way you'll treat the finished blouse, then measure the same line again. Enter the before and after lengths in Step 1 and the tool gives the shrinkage percentage, which you can carry straight into the buying calculation.
How much extra fabric should I buy?
Enough that, after shrinking, you're left with the length you actually need. The tool divides your finished length by one minus the shrinkage fraction — so for a 100cm finished length at 8% shrinkage you buy about 108.7cm. Pre-wash that cloth before cutting so the shrinkage happens on the roll, not on the stitched blouse.
Does fabric only shrink in length?
No — most fabric shrinks across the width too, and often by a different amount. Run the calculation once for the length and once for the width if the width matters to your layout. Pre-washing the full piece before cutting handles both directions at once.
Educational estimate only. Shrinkage depends on the fibre, weave, and wash; always test-wash your own fabric and pre-wash before cutting rather than relying on a typical figure.