🧵 Fabric Shrinkage Adjustment Calculator
Enter your fabric type and the measurement you want after washing, to see what size to cut before shrinkage.
Why it divides instead of adding a percentage
cut = desired finished / (1 - shrinkage% / 100)Cotton at 4% with a 40 in target gives 40 / 0.96 = 41.67 in. Check it: 41.67 x 0.96 = 40.00. Adding 4% instead gives 41.60 in, which washes down to 39.94 - short where it matters on a waistband. Wool at 10% needs 44.44 in of cloth to land on 40.
Working with the number
- Shrinkage runs by direction. Most wovens lose more along the lengthwise grain than across it, so a single figure cannot cover both. Run the tool once for length and once for width if the two differ.
- The presets are typical, not measured. Cotton 4%, linen 3%, wool 10%, polyester blend 2%. Your bolt may not agree - flannel and loosely knitted cotton can lose 8% or more. Test it: mark a 10 in square, wash and dry as you will treat the garment, then measure. A 9.6 in square is 4%.
- Seam allowance shrinks too. The output is a raw cloth dimension. Add your allowances to the pattern piece first, then apply the adjustment to the whole piece, allowances included.
Frequently asked questions
How much does 100% cotton shrink in the wash?
Around 3 to 5% for a stable woven washed warm and tumble dried, and more for flannel, gauze or jersey, which can reach 8 to 10%. Most of it happens in the first wash.
Do I add the shrinkage percentage or divide by it?
Divide. Shrinkage is taken off the cut size, not the finished size, so you need the number that is 4% smaller after washing rather than the number 4% larger than your target. Adding leaves you short every time.
Does pre-shrunk fabric still shrink?
Usually a little - 1 to 2% is common even on fabric sold as pre-shrunk, since mill finishing is not a domestic hot wash. Choose the pre-shrunk option only when your own test square has come back unchanged.