Fabric shrinkage.

Worked example

A 10 inch by 10 inch swatch washes and dries to 9.5 inches long and 9.7 inches wide. Length shrinkage = (10 - 9.5) / 10 = 5%; width shrinkage = (10 - 9.7) / 10 = 3%. A pattern calling for 3 yards needs 3 / (1 - 0.05) = 3.158 yards if you wash before cutting, which is 5.3% more. A 30 inch skirt cut from unwashed fabric would shrink to 30 x 0.95 = 28.5 inches long.

How it works

shrinkage % = (before - after) x 100 / before, measured separately along the length and the width. Yardage to buy = pattern yardage / (1 - length shrinkage). This is exact: after washing you keep bought length x (1 - shrinkage), and that must equal the pattern amount. It gives slightly more than simply adding the percent (5% shrinkage needs 5.3% extra, not 5%).

Rule of thumb vs this tool. The Fabricis guide suggests buying 10% more for cotton and linen and 5% more for bio-washed fabric or poly blends. That is a common rule of thumb, not a published standard; a swatch test on your own fabric is more accurate.

Wash the swatch the way you will wash the garment. If you will tumble dry, tumble dry the swatch. Only length changes the yardage; check the pattern width against your fabric after it has shrunk in width.

Sources and basis (all opened 2026-10-08): How to Calculate Fabric Shrinkage Percentage in Garment and Textile Industry? (Online Clothing Study) for the percent formula and its 100 to 95 example; Fabric Shrinkage Guide: How to Calculate & Pre-Wash (Fabricis) for the typical ranges (cotton 3% to 5%, linen 5% to 10%, rayon or viscose 5% to 10%+, polyester under 3%) and the 10% / 5% buying suggestion. Both are commercial guides, not standards.

FAQ

How do I calculate fabric shrinkage percentage?

Subtract the length after washing from the length before, divide by the length before and multiply by 100. A swatch that goes from 100 cm to 95 cm shrank 5%. Do it separately for length and width.

How much extra fabric should I buy to allow for shrinkage?

Divide the pattern yardage by 1 minus the shrinkage. For 5% shrinkage that is 5.3% more. As a rule of thumb, not a published standard, one guide suggests 10% extra for cotton and linen and 5% for bio-washed or poly blends.

Should I wash fabric before sewing?

If the garment will be washed, pre-washing makes the fabric shrink before you cut. Wash and dry it the way you will care for the finished piece, then press to realign the grain.

Which fabrics shrink the most?

One guide lists cotton at about 3% to 5%, linen at 5% to 10%, rayon or viscose at 5% to 10% or more, and polyester under 3%, with wool unpredictable. Your own swatch matters more than a table.

Does width shrinkage change how much fabric I buy?

Not the yardage, which depends on length. But if the fabric gets narrower, a pattern layout that just fit the original width may no longer fit, so check the usable width after washing.