Shrinkage is the change in fabric dimensions after washing, drying or steaming. Most shrinkage is a loss of length or width, though some fabrics grow in one direction. Uncontrolled shrinkage causes garments to change size after the first wash, which leads to returns and failed tests.
Why fabrics shrink#
Relaxation shrinkage#
During spinning, weaving, knitting and finishing, yarns and fabric are held under tension. When the fabric is wet and free to move, the yarns relax back towards a more natural state, and the fabric shrinks. This is the main cause of shrinkage in cotton and other cellulosic fabrics.
Swelling shrinkage#
Fibers such as cotton and viscose swell when wet. Swollen yarns take a longer path around each other, pulling the fabric shorter.
Consolidation shrinkage#
Repeated washing and tumble drying keep shaking the structure into a more compact state. Knits are especially prone.
Felting shrinkage#
Wool fibers have scales that lock together when agitated in water. Felting shrinkage can be large and is irreversible without special treatment.
Thermal shrinkage#
Synthetic fibers such as polyester and nylon shrink when heated above their heat-setting temperature. Heat setting at the finishing stage stabilises them.
Measuring shrinkage#
- Condition the specimen and mark reference distances (for example 50 cm) in length and width.
- Wash and dry to the specified method (such as ISO 6330 procedures for domestic washing, or AATCC 135 for fabric and AATCC 150 for garments).
- Condition again and re-measure.
A negative result means shrinkage; a positive result means growth. See dimensional stability testing.
Worked example#
Marks 50.0 cm apart in length measure 47.8 cm after washing. Width marks 50.0 cm apart measure 48.9 cm.
- Length: (47.8 - 50.0) / 50.0 × 100 = -4.4%
- Width: (48.9 - 50.0) / 50.0 × 100 = -2.2%
The shrinkage calculator does this and also gives a pattern allowance.
Shrinkage in knitted fabrics#
Knits are especially sensitive because loops can change shape freely. Length shrinkage is often higher when the fabric was stretched lengthways during wet processing and drying. Main controls:
- Stitch length and tightness: set at knitting.
- Relaxed drying: tumble or relax dryers that let the fabric shrink before finishing.
- Compaction: mechanical compacting reduces length shrinkage.
- Correct stenter settings: width and overfeed that do not overstretch the fabric.
Shrinkage in woven fabrics#
- Sanforising (compressive shrinkage) is used for cotton wovens such as denim and shirting to pre-shrink the fabric.
- Weft shrinkage depends on how much the fabric was stretched in width on the stenter.
- Garment washing (for denim and casual wear) adds shrinkage that must be allowed for in the pattern.
Pattern allowance#
If a fabric shrinks by a known amount and the garment will be washed after sewing, or the fabric cannot be improved, the pattern can be made larger to compensate:
For a finished length of 70 cm and 4% shrinkage: 70 / 0.96 = 72.9 cm.
This is used for garment-washed products. For garments sold unwashed, the goal is to keep fabric shrinkage within the buyer's limit instead of relying on pattern allowance.
Checklist#
- Shrinkage tested on bulk fabric before cutting, to the buyer's method
- Results compared with the buyer's limits for fabric and garment
- Pattern allowance decided for washed garments
- Finishing parameters recorded for good lots
- Garment wash test on the first bulk garments
For shrinkage failures, see excessive shrinkage.
Related guides#
- Spirality in knitted fabric: the twisting that often appears in the same wash test as shrinkage in single knits.
- Single jersey fabric: the knit fabric where shrinkage control matters most in volume production.
- Stretch and recovery: why stretch fabrics also need growth and recovery checks, not only shrinkage.
- Fabric defects: shrinkage alongside the other fabric problems to catch before cutting.
- Sustainable bio-scouring process: how gentler pretreatment is part of well-controlled wet processing.