Dimensional shrinkage
Shrinkage (%) = (before − after) ÷ before × 100
Each starting and final dimension must be greater than zero. A positive answer means shrinkage; a negative answer means growth. The interface displays the absolute percentage followed by “shrinkage” or “growth”. CSV records preserve the signed shrinkage value.
This shrinkage sign convention differs from a signed dimensional-change convention, where growth is positive. The size of the change is the same; the label matters. The same unit must be used on both sides of a comparison.
Area change
Area shrinkage (%) = [1 − (after length ÷ before length) × (after width ÷ before width)] × 100
This assumes a rectangular region. It does not measure skew or a distorted boundary. A 5% length loss and a 3% width loss yield 7.85% area loss, not 8%. Area is supporting information, not a substitute for checking both directions.
Reverse yardage
Minimum length before washing = (target usable length + extra usable length) ÷ (1 − length shrinkage ÷ 100)
The rate must be below 100%. The planning interface accepts rates down to −100% for mathematical growth comparisons but does not recommend buying less based on growth. Optional extra is a desired allowance after washing, not a second percentage uplift.
With a positive shop increment, divide the minimum by the increment, round upwards to a whole number and multiply by the increment. A tiny floating-point tolerance prevents an exact boundary such as 2.00 metres being rounded to 2.25. All planning uses unrounded measurements; display rounding never replaces the underlying calculation.
Units and precision
1 inch = 2.54 centimetres and 1 yard = 0.9144 metres. Changing units converts existing values. Display precision does not imply the sample was measured that accurately. Printed and exported results need to be read alongside the measurement method.
Limits
- A sample result may not repeat across a whole length, another batch or repeated care cycles.
- We do not predict rates from fibre, temperature, weave, finish or dryer settings.
- The tool does not prescribe care, optimise pattern layouts or certify garment fit.
- Skew, colourfastness, texture and seam behaviour are not measured.
- This is not an AATCC or ISO test procedure or laboratory certification.
Sources and editorial status
Cotton Incorporated’s CottonWorks guide is the technical background for why construction and processing affect dimensional change. Pattern Scissors Cloth’s swatch-testing article is a practical further reading example for swatch preparation. Neither source has endorsed or reviewed this site.
All worked numbers on this site are original illustrative calculations. CHEN operates and maintains Swatch Ledger with AI-assisted drafting and implementation. No independent textile specialist has reviewed this release. Report a reproducible error at ad@random-walk.co.jp.
Sources and formulas checked: 30 September 2026. Review is triggered by a reported error, calculation change, source change or material browser issue.