How do you test garment shrinkage after washing?

The two methods buyers ask for

AATCC 135 is the American route and is what a US buyer will normally request. ISO 6330 with ISO 5077 is the European equivalent. Both do the same thing: a defined wash, a defined dry, a measured change. The test is only comparable if the wash temperature, detergent and drying method are stated alongside the result.

Care labels matter here. A garment tested at 40 °C and tumble dried will shrink noticeably more than the same garment washed at 30 °C and line dried. Quoting a shrinkage figure without the test conditions is meaningless.

Why length moves more than width

In a knitted panel the loops are pulled along the length during finishing, so the length has more stored distortion to release in the first wash. Width is held by the Wales of the knit and moves less. This is why a hoodie can lose 4 cm of body length and almost nothing across the chest.

Garment dyeing and washing add a second shrink on top of the fabric shrink. A piece that was already garment washed needs its own test, not the greige fabric result.

What we do with the number

The result goes into the pattern as an allowance before bulk cutting, and into the care label as the wash instruction the garment can survive. If a fabric fails the target, the options are compaction at the mill, a pre-shrink wash, a blend change, or a pattern allowance — in that order of cost.

For repeat orders we re-test whenever the mill changes lot or finish, because the same quality code from a different lot can shift half a percent.