Fabric Shrinkage Calculator

Natural fibers shrink when they first encounter water and heat. If you cut and sew a garment from unwashed fabric, it will shrink the first time you launder it — and the fit you worked so hard on will be gone. Pre-washing (also called pre-shrinking) gets the shrinkage out before you cut.

Always pre-wash the way you plan to launder the finished garment.If you'll machine wash warm and tumble dry, pre-wash the same way. If you'll dry clean, you can skip pre-washing (but still steam-press to pre-shrink steam-sensitive fibers like wool).

Cut a swatch at least 10" × 10" (25 × 25 cm). Mark a precise square with a ruler and fabric marker. Wash and dry it, then re-measure. The difference gives you the exact shrinkage percentage for that specific fabric, dye lot, and wash method.

Length and width can shrink at different rates — especially in knits, where length often shrinks more than width. The calculator measures both independently.

Linen can shrink 5–10% and may continue to shrink for several washes. Consider washing and drying twice before cutting. The fabric also softens dramatically after washing, which may be desirable.

Raw/unwashed denim can shrink up to 10%. Sanforized denim (pre-shrunk at the mill) shrinks much less (1–3%). Check the bolt information.

Woolcan felt (mat and shrink irreversibly) if machine-washed with agitation. Pre-shrink wool by steam pressing with a damp cloth (the "London shrink" method), or by soaking in cool water without agitation.