Cotton Fabric Shrinkage: How Much to Expect, How to Test It and What to Allow

What is fabric shrinkage?

Shrinkage is how much smaller a cloth becomes after washing, given as a percentage of its size before washing. It is measured in two directions, along the warp for length and across the weft for width, and the two figures are usually different. A specification that gives one shrinkage figure is giving the larger of the two, or an average, so ask which.

Why does cotton shrink?

Cotton yarn is pulled straight and held under tension while it is spun, woven and finished, and the cloth leaves the mill slightly stretched. In water the fibres swell and the yarns relax into a shorter, more crimped path. That relaxation is most of the shrinkage, and it happens on the first wash. Later washes add smaller amounts as the fabric settles, which is why a shrinkage figure is quoted after a stated number of washes.

How is shrinkage measured?

Lay the cloth flat and draw a square on it, 50 by 50 cm, with one side along the warp. Wash and dry it the way the finished garment will be washed, then lay it flat again and measure the square. Shrinkage in each direction is the loss divided by the original 50 cm, times 100. A square that comes back at 48.5 cm along the warp and 49 cm across the weft has shrunk 3% in length and 2% in width.

Sanforized and other pre-shrunk finishes

Sanforizing is a mechanical finish that compresses the cloth lengthways between a rubber belt and a heated cylinder before it is sold, so the relaxation that washing would cause has already happened. A sanforized cloth is designed to show a residual shrinkage of about one per cent or less. Other pre-shrinking routes, such as washing the cloth at the mill, aim at the same result by a different method. The finish line on our product pages and swatch cards says what the cloth had, and the shrinkage figure is the number to ask for alongside it.

How much should you allow when cutting?

Take the shrinkage figures for the cloth you are cutting and add them to the pattern in each direction, or cut on a cloth that has already been pre-shrunk. On our 57 to 58 inch Piece Dyed Texture Dobby 9072G, 3% shrinkage across the weft takes about 1.7 inches off the width, which changes how many pattern pieces fit across a marker. Measure a sample from the actual roll, because two cottons with the same count and construction can shrink differently if their finishes differ. How to read the finish and the other lines on a specification is covered in how to read a woven fabric specification.