Work out fabric shrinkage allowance instantly with clear inputs, formula shown and shareable results.
To finish at a target dimension after shrinkage, the cut dimension must be the finished value divided by (1 - shrinkage fraction), not multiplied by (1 + shrinkage). The distinction matters: 5% shrinkage needs a 5.26% allowance, and the error compounds across both directions in area terms.
Shrinkage allowance
Cut dimension = finished dimension / (1 - shrinkage %)
Shrinkage is measured as a loss from the original size. Adding 5% to the finished size then losing 5% of that larger figure leaves you short — the correct inverse is division.
By marking a known distance on the fabric, laundering to the specified standard, then re-measuring. Test both directions and after multiple wash cycles, since much shrinkage occurs in the first two washes but not all.