Fabric Shrinkage by Fiber Calculator — Pre-Wash Prediction

Untreated 100% cotton typically shrinks 3-5% in length and 2-3% in width on the first wash in warm water. Pre-shrunk cotton shrinks less (1-2%). Tumble drying increases shrinkage further. Always pre-wash cotton before cutting your project.

Yes, hotter water causes more shrinkage. Cold water (30°C) causes about 30% less shrinkage than warm water (40°C). Hot water (60°C) causes about 40% more shrinkage. The first wash causes the most shrinkage; subsequent washes cause minimal further change.

If you plan to tumble dry the finished garment, yes. Tumble drying typically adds 20-30% extra shrinkage on top of the wash shrinkage. If you will always hang dry the finished item, pre-wash without tumble drying.

It depends on the weave. Many woven fabrics shrink a little more along the length (warp) than the width (weft) because the warp yarns sit under more tension on the loom — this calculator uses that as its default. But the direction that shrinks most is actually governed by yarn density: if a fabric has higher weft (width) density it can shrink more across the width instead. There is no fixed 1.5-2x rule, so cut a 20×20 cm swatch, wash and dry it exactly as you will treat the finished item, then re-measure both directions. Use the Custom fibre option to enter your own length and width figures from that test.