A shirt is cut to a size, sewn, washed, and comes out smaller. If the fabric shrinks, a garment
cut at its finished size is a size too small after the first wash, and a customer who bought a
large has a medium. The cure is to cut bigger. How much bigger is a measurement, not a
guess, and it can change how many garments fit across the cloth.
Measure the shrinkage first
Shrinkage is different in length and in width, and different for every fabric, so it is
measured on the fabric you are about to cut:
- Mark a square on a swatch, say 50 cm × 50 cm, with a fabric marker or stitched
marks.
- Wash and dry it the way the finished garment will be treated, the way the label says.
- Measure the square again, in each direction.
- Shrinkage in that direction is (50 − measured) ÷ 50. A square that comes out
at 48.5 cm has shrunk 3%.
Do it on at least two swatches from the roll. The roll in your hand is the evidence; the
figure on the supplier's sheet is a claim about a different roll.
The sum
Cut size
finished size ÷ (1 − shrinkage).
It is a division, not a multiplication by 1.03. With 3% shrinkage, the cut size is the finished
size divided by 0.97, which is 3.09% bigger, not 3%. The difference is small on one garment
and real on a bulk order.
A worked example
These figures are made up to show the sum. They are not a benchmark and not a claim about any
fabric. The garment and fabric are the ones the
fabric consumption calculator opens with, and the
fabric consumption article works through: a
usable width of 112 cm, a widest point of 55 cm, a longest piece of 110 cm plus 60 cm for
sleeves, collar and facings, 8% wastage, ₹250 a metre. Without shrinkage that is
0.918 m a garment, ₹229.50, with two garments across the width.
Now say the swatch test gave 3% shrinkage in length and 1% in width.
- Widest point, cut size: 55 ÷ 0.99 = 55.56 cm.
- Length, cut size: (110 + 60) ÷ 0.97 = 175.26 cm, instead of 170.
- Across the width: 112 ÷ 55.56 = 2.016, so two still fit.
- Each garment takes 175.26 ÷ 2 = 87.63 cm, and with 8% wastage, 94.64 cm:
0.946 m, ₹236.60.
Allowing for shrinkage costs ₹7.10 a garment here, which is 3.1% more fabric. On an order
of 50 the fabric bill goes from ₹11,475 to ₹11,830.
When it tips over a cliff
Change only the width shrinkage, from 1% to 2%. The widest point, cut size, is
55 ÷ 0.98 = 56.12 cm. Across the width: 112 ÷ 56.12 = 1.996, which
is less than two. Only one garment fits across.
By this simple rule, each garment now takes the whole 175.26 cm, and with wastage 189.28 cm
— 1.893 m, ₹473.20. One point of width shrinkage has doubled the
fabric. The fabric bill for 50 goes to ₹23,660.
The tipping point is exact: two garments fit across only while the width shrinkage is under
1.79%. Above that, a whole garment-width is lost.
Shrinkage can change the layout, not just the length
A small percentage that pushes a piece over the width of the cloth costs far more than the
percentage suggests. Check the cut width against the usable width before you check anything
else.
What if you ignore it?
Cut at the finished size and a 2% width shrinkage turns a 55 cm flat width into 53.9 cm,
which is a chest 2.2 cm smaller. A 3% length shrinkage takes a 110 cm piece to 106.7 cm. The
garment is out of its size, and the cost of that appears as returns and rework, not as a line
on the costing sheet. See the
rejects and rework article.
What to do with it
- Test every fabric, every roll batch, before the pattern is finalised.
- Test in length and in width. They are rarely the same.
- Put the shrinkage in the pattern, as a larger cut size, not as a note on
the cutting sheet that someone has to remember.
- Re-run the fabric consumption with the cut sizes, not the finished ones.
The marker planning article shows how the
layout and the wastage depend on it.
What the sums leave out
- Made-up shrinkage and garment. 3%, 1% and 2% are assumptions. Measure your
own.
- A simple layout rule. The sum counts whole garments across the width. A
real marker can interlock pieces and may rescue part of a cliff like the one above, at a cost
in wastage that only the marker will show.
- Different wash, different shrinkage. A garment washed hot shrinks more
than the one tested warm. Test the way it will be washed.
- Shrinkage after the first wash. Some fabrics keep shrinking a little. A
single test does not show that.
Put the cut sizes into the fabric consumption calculator and the cost
into the costing sheet. The
fabric line is quietly decided here, before anything is cut.