Does cotton shrink when you wash it?

Yes. Moda Fabrics says quilting cotton shrinks between 3 and 5 percent, and mostly across the width. Kokka Fabrics puts cotton at around 5 percent and says up to 10 percent is not uncommon for some fabrics. Flannel can shrink more than regular quilting cotton. That is why garments and washable home pieces are usually cut from prewashed fabric.

Should you prewash fabric before quilting?

It depends on the look you want and the pieces you are using. Prewash yardage and fat quarters if the quilt will be tumble-dried and you want it to stay flat, and prewash saturated reds or dark colors that sit next to white. Skip it for charm packs and jelly rolls, which fray and lose their square in the wash, or if you want the crinkled look a quilt gets when unwashed fabric shrinks around the stitching.

Should you prewash precut fabric like jelly rolls and charm packs?

Usually not. Moda says washed kit pieces shrink and come out straight on the grain but not square for cutting. If you need to wash them, Moda uses mesh laundry bags that aren't overstuffed, a gentle cycle with minimal spin and pressing afterward, and suggests test-washing a couple of strips first.

Does polyester fabric need to be prewashed?

Not for shrinkage. Kokka Fabrics says synthetics like polyester and nylon will not shrink, but it still recommends a prewash to remove leftover finishing chemicals and any loose dye that could bleed later.

How do you stop fabric dye from bleeding when you prewash?

Wash saturated reds, purples, dark blues and greens on their own or with similar colors, add a dye-trapping sheet such as a Shout Color Catcher to catch loose dye in the water, and take the fabric out of the machine as soon as the cycle ends so wet dark fabric isn't resting on light fabric. If a swatch keeps releasing dye, rethink pairing it with white.

Should You Prewash Fabric? How Much Cotton Shrinks

Yes, cotton shrinks, and the people who weave it will tell you roughly how much. The real question is whether it shrinks before you cut or after you have sewn. Wash first and the fabric settles while it is still a flat rectangle. Skip it and the first laundry cycle does the settling inside your seams.

Precuts, a quilt you want crinkled and anything that will never be washed can skip the step. Here is what the fabric makers publish, and how to decide.

How much each fiber shrinks, according to the people who make it

Every figure comes from the fabric maker or fiber body named in its row. Where a maker publishes no number, the table says so.

Fiber	What the maker publishes	Source	Prewash it?
Quilting cotton	Shrinks between 3% and 5%, mostly across the width	Moda Fabrics	Yes, if the finished piece will be washed
Cotton garment fabrics	Around 5%, and up to 10% is not uncommon for some fabrics	Kokka Fabrics	Yes, the way you will wash the finished piece
Cotton flannel	Can shrink even more than quilting cotton; no figure given	Moda Fabrics	Yes
Cotton batting (Warm & Natural)	3% in a cold first wash, 5% in warm water	The Warm Company	No. The maker says prewashing is not necessary
Rayon and lyocell	A tendency to shrink and to bleed color; no figure given	Kokka care guide	Yes, cold, then air-dry
Linen	The makers disagree: Moda says linen shrinks like cotton, Kokka's care guide says it won't shrink in the machine	Moda, Kokka	Yes, on a cool wash, and run the swatch test below
Untreated wool	Felting shrinkage that cannot be reversed; no figure given	The Woolmark Company	Keep it out of washer agitation and the dryer unless it is labelled machine washable
Polyester and nylon	Will not shrink	Kokka Fabrics	Optional. Kokka still prewashes to remove finishing chemicals and loose dye

A range is not your fabric. Moda notes that different weaves shrink differently, even within cotton. The swatch test below tells you about the bolt on your table.

Moda also says the loss can reach a couple of inches across the width. That matters when a pattern layout only just fits your fabric width, so check the fabric requirements on the envelope before you buy (how to read a sewing pattern walks through that grid).

Prewash or skip it? Decide by the project

What you are making	Prewash?	Why
Garments: a shirt dress, skirts, trousers	Yes	Fit is fixed at cutting. A shrunken collar pulling against its interfacing cannot be pressed out
Washable home pieces: a pillowcase, a tote bag, napkins	Yes	They go in the laundry, so the shrink should happen before the seams exist
A quilt from yardage or fat quarters	Your call; yes if it will be tumble-dried	Prewashed pieces stay flat. Unwashed ones give the crinkled look when the finished quilt is washed
Charm packs, jelly rolls, layer cakes	Usually no	Small pieces fray, and washed pieces come out straight on the grain but not square for cutting
A pouch, wall hanging or anything never washed	Skip it	Kokka says you can skip it for pieces you don't plan to wash
Dry-clean-only fabric	Skip it	Seamwork's rule is to always prewash unless the fabric can only be dry-cleaned

A pillowcase or tote from what to sew first is a good place to practise the routine.

How to prewash without losing fabric

1. Finish the raw edges

Unfinished woven edges fray in the machine and tangle into a knot of threads. Seamwork's prewash experiment warns you can lose a few inches of yardage that way. It rated serging as the most secure finish, with zigzag and pinking close behind. No machine handy? Kokka bastes the edges and adds a mesh laundry bag.

2. Wash it the way you will wash the finished piece

This is the rule every source agrees on. Kokka's guide says to use the same method you plan to use later, on the gentlest cycle, and Utah State University Extension tells its pillowcase makers to wash before cutting to eliminate shrinkage and remove excess dye. If the finished piece will realistically be tumble-dried, tumble-dry the fabric too.

3. Dry, then press

Kokka squeezes out the water without wringing, air-dries until the fabric is about half dry, then presses. A steam iron gets it flat enough to square up.

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Precuts and quilts play by different rules

Precuts are cut to exact sizes, and that is the problem. Moda says it would not prewash kit pieces unless they were generously cut, because they shrink and come out of the wash on grain but not square. If you do want to wash them, Moda's precut method is mesh laundry bags that aren't overstuffed, a gentle cycle with just enough spin to remove water, and pressing afterward. Test a couple of strips first. Pinked edges help, but Moda says minimal fraying is not guaranteed.

Fairfield takes the other route: sew the precuts together and wash the finished project, with a lingerie bag for small pieces like fat quarters.

Fat quarters are a different story: the quilted lap throw project has you prewash them if the quilt might ever be tumble-dried. Skip the wash and the finished quilt shrinks around its stitching instead. Moda calls that the soft, crinkly, quilty look, and plenty of quilters want it. Pair unwashed cotton with a cotton batting like Warm & Natural and The Warm Company's 3% cold or 5% warm figure becomes a design choice.

Dye bleed is a separate problem

A fabric can hold its size and still release dye. Moda names the usual suspects: highly saturated reds, purples, dark blues and greens. Kokka singles out red and washes it alone.

Prewash strong colors headed next to white. Moda would prewash a batik or saturated red that is going into a quilt with white.
Add a dye-trapping sheet. Shout Color Catcher sheets absorb and trap loose dye released during the wash. Shout's directions call for two sheets in a load with new or heavily colored fabric. Moda's precut method uses one when colors are saturated.
Take it out the moment the cycle ends. Moda warns that wet dark fabric resting on wet white fabric can transfer dye.

A sheet is not a fix. It catches loose dye in the water; it doesn't change the fabric. If a swatch keeps staining, rethink putting it next to white.

The measure-before-and-after test

Published ranges get you started. Your own swatch settles it for the fabric you bought.

Cut a swatch from the yardage, not the frayed end.
Mark a square well inside the cut edges with a marker that survives water, so fraying can't pass for shrinkage.
Note which way the selvage runs, then measure the square along the length and across the width without stretching it.
Wash and dry the swatch exactly the way you plan to wash the finished item.
Let it dry completely and press it without pulling, then measure both directions again.
Compare each direction separately. Moda says fabric shrinks mainly in the width, so don't average the two.

If the square barely moved, great. If it moved in one direction, buy extra fabric in that direction, or wash the whole length before cutting.

After the wash: square up, then cut

Washed fabric rarely comes out square. Press it, fold it selvage to selvage, and trim one clean edge before you measure anything. A rotary cutter, a self-healing mat and a long quilting ruler make that one straight cut quick, though sharp scissors along a pulled thread work too.

Then cut. A slightly wonky pillowcase that keeps its size wash after wash is a good pillowcase. Wonky seams are the whole point.