What Is a Fabric Shrinkage Calculator?
Almost every woven or knit fabric shrinks the first time it's washed, because the manufacturing process (spinning, weaving, dyeing) stretches fibers slightly and washing lets them relax back toward their natural size. This calculator applies a known shrinkage percentage to a garment's pre-wash length and width so you can predict its finished size before you cut, sew, or buy.
It's especially useful for sewists cutting a pattern from fabric that hasn't been pre-washed, and for shoppers comparing a size chart's "as sewn" measurements to what a garment will actually measure after its first wash.
How to Read Your Results
Post-Wash Length & Width
These are the predicted finished dimensions after the fabric shrinks by the entered percentage. They're calculated independently, since a fabric's shrinkage rate is usually similar along both the length (warp) and width (weft) grain, though some fabrics shrink more in one direction.
Length Lost & Width Lost
The actual number of inches removed from each dimension — useful for deciding how much extra fabric to buy or how much larger to cut a pattern piece.
Approximate Area Shrinkage
Because both length and width shrink at the same time, the total area shrinks by more than the linear percentage. This figure is helpful when estimating how much extra fabric yardage to purchase overall.
Real-World Example
A 30" × 20" piece of quilting cotton with a typical 5% shrinkage rate:
| Dimension | Pre-Wash | Post-Wash |
|---|---|---|
| Length | 30.0 in | 28.5 in |
| Width | 20.0 in | 19.0 in |
| Area | 600 sq in | ≈541.5 sq in |
Even though the linear shrinkage is only 5%, the piece loses about 9.75% of its total area — a difference that matters when you're calculating exactly how much fabric to buy for a project.
Tips for Managing Fabric Shrinkage
- Pre-wash fabric before cutting so shrinkage happens before your pattern pieces are sized, not after.
- Match your wash test to how you'll actually launder the finished item — a cold, gentle wash shrinks less than a hot wash and hot dryer.
- Cotton and rayon shrink the most; polyester and other synthetics typically shrink the least.
- Wool can shrink dramatically (felt) if agitated in hot water — always check the care label first.
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Last updated: August 2026 · Reviewed by: Simple Calculator Tools Editorial Team