Entry 05 · shrinkage
Fabric shrinkage calculator
Wash a test swatch, measure it before and after, and find out how much the fabric shrinks and how much extra to cut or buy.
Wild Linen Lab · fabric shrinkage
For your project
- Cut 210.5 cm (2.11 m) before washing to end up with 200 cm (2 m): 10.5 cm extra.
- Buy 220 cm (2.2 m), rounded up to the nearest 10 cm.
- After washing, 140 cm (1.4 m) wide fabric is about 137.2 cm (1.37 m) wide.
How to measure shrinkage
- Cut a square of at least 50 × 50 cm (20 × 20 in) from your fabric. Laboratories work the same way: ISO 3759 asks for a 500 mm square with marks at least 350 mm apart.
- Mark a 35 cm (14 in) distance in each direction with a laundry marker or tacked thread, at least 5 cm (2 in) from the edges, because cut edges fray and distort.
- Wash and dry the swatch exactly as you will treat the finished item, including the dryer if you will use one.
- Measure between the marks again and enter both sets of figures.
The results. Shrinkage is (before − after) ÷ before × 100, the same formula as the ISO and AATCC tests. To finish with a given length, cut the length ÷ (1 − shrinkage). The buying figure is rounded up to what shops cut: 10 cm, or an eighth of a yard. The width line shows how wide the fabric will be after washing, and warns if that is narrower than your layout needs.
No swatch? "Typical figure" uses the top of a published range for the fibre. Treat it as an estimate: finishes vary a lot.
Worked example. A 50 cm swatch of cotton measures 47.5 cm lengthwise and 49 cm widthwise after washing: 5% and 2%. Curtains that must be 200 cm long after washing need 210.5 cm cut, so buy 2.2 m, and 140 cm wide fabric ends up about 137 cm wide.
Typical shrinkage by fibre
Published figures vary with the fabric's construction and finish, and the sources don't all measure the same thing, so read these as rough guides rather than predictions.
| Fabric | Shrinkage | Kind of figure | Source |
|---|---|---|---|
| Woven cotton, linen or canvas | 2–7% | rule of thumb | OnlineClothingStudy (Prasanta Sarkar) |
| Linen, not pre-washed | 7–10% | rule of thumb | fabrics-store.com product answers |
| Cotton jersey, factory finished | about 4.5–7.3% long, 3.5–6% wide | mill trial | Cotton Incorporated, ISP 1009 |
| Rayon (viscose) | 5–10% | rule of thumb | OnlineClothingStudy; Sewing & Craft Alliance ("as much as 10%") |
| Woven wool, Woolmark certified | no more than 3% | industry limit | Woolmark specification AW-1 (woven apparel) |
| Polyester | about 0% | rule of thumb | OnlineClothingStudy |
Sources
- ISO 3759:2011, Textiles: Preparation, marking and measuring of fabric specimens and garments in tests for determination of dimensional change (publisher's preview): specimen size, mark spacing and the formula.
- AATCC, TM135, Dimensional changes of fabrics after home laundering.
- Cotton Incorporated, ISP 1009: Guide to improved shrinkage performance of cotton fabrics: knit shrinkage before and after finishing, and how much one wash removes.
- The typical-figure sources are linked in the table above.
Questions
Should I pre-wash fabric before sewing?
If the finished item will be washed, yes: wash and dry the fabric the way you will treat the finished piece, then cut. Most of the shrinkage happens straight away; Cotton Incorporated notes that one wash cycle may remove around 90% of the shrinkage available in cotton.
Why is lengthwise shrinkage different from widthwise?
Yarns are held under tension during weaving, knitting and finishing, and washing lets them relax, so the two directions rarely shrink alike. In wovens the length often shrinks more; knits can go the other way, as in Cotton Incorporated's trial, where unfinished single jersey shrank more in width than in length.
My swatch got bigger. Is that possible?
Yes. Some fabrics relax and grow slightly, especially in one direction. The calculator shows that as growth, and still tells you to buy at least the length your pattern asks for.
How big should the test swatch be?
Bigger is more accurate, because a millimetre of measuring error matters less. Laboratory methods use a 500 mm square (ISO 3759) or a 38 cm square with 25 cm marks (AATCC TM135). At home, 50 × 50 cm or 20 × 20 inches with marks 35 cm or 14 inches apart works well.