Illustrative situation
A supplier sends a test report showing "-4.5 / -2.0" for a T-shirt. The buyer is unsure what the numbers refer to, whether they are good, and whether they compare with another supplier’s report.
Main answer
A shrinkage percentage tells you very little until you know the test method, the washing and drying conditions, the number of cycles and which direction each number refers to. Usually the first value is length and the second width, a negative sign means shrinkage and a positive sign means growth, but always check the report’s own key.
Find the method first
The report should name a standard, such as ISO 5077 for dimensional change in washing and drying or AATCC TM135 for dimensional changes of fabrics after home laundering. It should say whether the test was on fabric or on a finished garment. Garment-based methods, such as AATCC TM150 for dimensional changes of garments after home laundering, can give different results from fabric tests.
Check the conditions
ISO 6330 specifies domestic washing and drying procedures, including reference machines, detergents and six drying options such as line dry, flat dry and tumble dry. Different procedures give different results, and the standard itself notes that machine type, detergent and dryer can affect results. A report should state the programme, temperature and drying method, and the number of cycles.
Read the numbers
Look for the direction labels, usually length or warp and width or weft for woven fabrics, and wales and courses for knits. Note the sign and whether the value is an average of several specimens. A figure of minus 4.5 percent in length means the sample became 4.5 percent shorter, assuming the report uses the usual sign convention. Check whether the measurement was taken after one wash or several.
Compare reports properly
Only compare reports made by the same method, conditions and number of cycles on the same fabric or garment. Ask the supplier to repeat the test under your conditions if needed. Decide your acceptable limits and write them into the quotation. See products on T-shirts and hoodies.
Fact, recommendation, uncertainty
- Established fact
- ISO 6330 defines domestic washing and drying procedures and notes that machine, detergent and dryer type can affect test results.
- Recommendation
- Check method, conditions, cycles, direction and sign before judging a shrinkage figure, and compare only like with like.
- Uncertainty
- Sign conventions and layout differ between laboratories, so the report’s own key is the final authority.
Sources and further reading
- ISO 5077:2007 — Determination of dimensional change in washing and drying
- AATCC TM135 — Dimensional Changes of Fabrics after Home Laundering
- ISO 6330:2021 — Domestic washing and drying procedures for textile testing
Sources checked on 24 October 2026. Standards bodies sell the full texts; we cite what their public pages state. General information, not legal or technical certification advice.
More perspectives from the team
Three further views on the same question, each by function. They add conditions and limits to the main answer; they are editorial notes, not customer reviews.
Sino Finetex Editorial Team Sourcing
Ask suppliers to quote shrinkage using the same method and conditions so figures can be compared. Limit: a supplier may not have the same machine, so agree a laboratory. Ask whether the report was issued by an independent laboratory or by the factory’s own lab.
Sino Finetex Editorial Team Product selection
Match the test conditions to how your customers wash, such as cold wash and line dry or warm wash and tumble dry. Limit: one test cannot cover every habit. Check the garment’s length and width limits against the fit you want after washing.
Sino Finetex Editorial Team Quality & care
Keep reports by lot number and compare with the approved reference. Limit: a report from an earlier lot does not cover a new one. Check that the specimen count and the date of the test are stated on the report.
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