Fabric Shrinkage Calculator

Frequently Asked Questions

How is shrinkage percentage calculated?

Shrinkage % = (pre-wash − post-wash) ÷ pre-wash × 100. A 36 in piece that comes out 34.2 in shrank (36 − 34.2) ÷ 36 × 100 = 5%.

How much fabric do I buy to allow for shrinkage?

Pre-shrink size = target ÷ (1 − shrink%). To end up with 60 in after a 5% shrink, buy 60 ÷ (1 − 0.05) = 63.2 in. Round up to the next quarter yard for safety.

What shrinkage should I expect by fabric?

Quilting cotton 3–5%, denim 5–10%, linen 8–12%, wool 0–5% (much more if felted), polyester near 0%, rayon 5–10%. Knits often shrink more in length than width.

Should I always pre-wash?

Pre-wash any garment or quilt fabric that will be laundered later, using the same heat and detergent the finished item will see. Skip pre-washing only for dry-clean wool tailoring or laminated/coated fabrics that lose their finish.

Provided by AllCalculators.io
Free online calculators for everyday. No registration required.

Estimates for informational purposes only.

Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.

JavaScript is required to use the interactive calculator above. The questions and answers below remain readable without JavaScript.

How This Calculator Works

Almost every natural fibre and many blends shrink the first time they are washed and dried, and a garment cut from loom-fresh fabric can come out of its first laundering a full size smaller, with seam allowances eaten away and a hem too short to let down. This calculator does the two jobs that prevent that. In measure mode you mark a known distance on a test piece, wash and dry it exactly as the finished garment will be treated, measure again, and it returns the true shrinkage percentage - the number no fabric label reliably gives you. In known-percentage mode you enter a shrinkage figure (from a test, a reference table, or the bolt) and a target finished size, and it returns the larger pre-shrink dimension you must cut or buy so the piece lands at the right size after washing. Either way it converts the percentage into the extra fabric allowance you need, turning a vague "allow a bit extra" into a measured number you can mark on the cutting table.

Formula / Method

Shrinkage% = (before − after) ÷ before × 100, measured over the same marked distance before and after a wash-and-dry cycle. The pre-shrink size is not the finished size plus that percentage - it is finished ÷ (1 − shrinkage% ÷ 100), because the percentage is taken of the larger original. The extra allowance to add is therefore pre-shrink − finished. Measure mode requires before and after both positive with after not exceeding before (fabric shrinks, it does not grow on a hot wash); known mode requires the percentage between 0 and 100% and a positive finished size. Any blank or out-of-range entry skips the calculation, so the result is never NaN and never tells you to cut a negative or impossible length. Measure warp and weft separately - lengthwise and crosswise shrinkage commonly differ.

Worked Example

You mark 20 inches on a swatch of cotton, wash and tumble-dry it, and it now measures 19 inches. Shrinkage = (20 − 19) ÷ 20 × 100 = 5%. You need a finished panel 36 inches long. Pre-shrink size = 36 ÷ (1 − 0.05) = 37.89 inches, so cut it about 37⅞ inches and it will shrink to 36 after the first wash. Notice that naively adding 5% (36 × 1.05 = 37.8) lands you slightly short, because the percentage was of the larger original - the divide-by formula is the correct one. With a known 4% figure and a 36-inch target, pre-shrink = 36 ÷ 0.96 = 37.5 inches, an allowance of 1.5 inches to add to that dimension.

Common Mistakes

Adding the percentage to the finished size instead of dividing - it under-allows, and the error grows with higher shrinkage.

Testing the swatch on a gentle cycle but laundering the garment hot, so the real shrinkage exceeds the measured figure.

Assuming warp and weft shrink equally; lengthwise shrinkage is often larger, so measure both directions.

Skipping the dryer in the test when the garment will be tumble-dried - heat-set shrinkage is usually the bigger component.

Pre-shrinking the fabric but not the lining, interfacing, or trim, so they pull or pucker after the first wash.

Tips & FAQ

How big should the test swatch be? At least a foot square with the measured marks well inside the edges, so fraying does not corrupt the after measurement. Which fabrics shrink most? Untreated cotton, linen, rayon, and wool can lose 3–10%+; many do most of it in the first wash, some keep creeping for several. Should I just pre-wash everything? Pre-washing washable fabric before cutting is the simplest fix and removes sizing too - this calculator is for when you cannot, or want to size the bolt purchase before pre-washing. Why measure both directions? Crosswise and lengthwise shrinkage differ, so a square cut piece can come back rectangular - allow each axis separately. What about "pre-shrunk" labels? They mean reduced, not zero; a residual 1–3% is common, so still test anything fitted. Does this apply to quilting cotton? Yes - mixing pre-washed and loom-fresh fabrics in one quilt causes uneven puckering after the first wash; treat all the cottons the same way.

Fabric Shrinkage Calculator

Frequently Asked Questions

Related Sewing Calculators