How Much Extra Fabric Should You Buy to Allow for Shrinkage?

If a fabric is going to shrink, the time to deal with it is at the counter, not after the first wash. Buy too little and you either cut pieces that come out undersized or end up short after pre-washing. Buy a sensible allowance and the problem disappears. This guide shows how to work out that allowance in two steps: first how much fabric the project needs, with the Fabric Yardage Calculator, then how much more to buy so that you still have that much after washing, with the pre-cut mode of the Fabric Shrinkage Calculator. It also covers the step most people miss: width shrinkage.

Step 1: how much fabric the project needs

Start from the area of fabric the project needs, including seam allowances and hems. Pattern envelopes give a length for each fabric width; for your own designs, add up the areas of the pieces. The yardage calculator turns that area into a length to buy: area divided by the usable width, plus a waste allowance for the gaps between pieces when you lay them out.

Take a project that needs 6 m² of fabric, cut from a 150 cm fabric with about 140 cm usable once the selvedges are trimmed, with a 15% waste allowance. The calculator gives:

• 4.29 m before waste;
• 4.93 m with the waste allowance, or 5.39 yards.

That is the length you need after any shrinkage has happened. The next step works backwards to the length to buy.

Step 2: allow for length shrinkage

If you know, or have measured, that the fabric shrinks by a certain percentage along its length, the length to buy is the length you need divided by (1 minus the shrinkage as a fraction). The shrinkage calculator's pre-cut mode does that. For the 4.93 m above:

• at 5% shrinkage, buy 5.19 m, an extra 0.26 m;
• at 3% shrinkage, buy 5.08 m, an extra 0.15 m.

It is tempting to add 5% of 4.93 m and stop there. That is slightly too little, because the 5% applies to the longer, unwashed length. On small amounts the difference is a few millimetres; on long lengths, such as several curtain drops, it adds up.

Step 3: do not forget the width

Fabric shrinks across its width too, usually by a different amount. Width shrinkage does not change how much length you buy directly, but it does reduce the usable width, and a narrower fabric needs more length for the same area.

Suppose this fabric also shrinks 2% across the width. 140 cm of usable width becomes 137.2 cm after washing. Running the yardage calculator again with 137.2 cm gives 5.03 m with waste, instead of 4.93 m. Then allow for 5% length shrinkage on that: the pre-cut mode gives 5.29 m to buy.

So for this project the honest answer is about 5.3 m, compared with the 4.93 m you would have bought ignoring shrinkage. That is roughly 7% more fabric, from two modest-sounding shrinkage figures. Width shrinkage matters most when pattern pieces only just fit across the fabric: a piece that fitted across 140 cm may no longer fit across 137.2 cm, which would change the layout entirely.

Where the shrinkage figure comes from

In order of reliability:

1. Your own wash test on a sample of the actual fabric, washed and dried the way the finished item will be. The guide to measuring shrinkage with a wash test explains how.
2. The mill's or supplier's specification, if it states shrinkage after a named wash in each direction.
3. Experience with the same fabric from the same supplier.
4. A general allowance for the fibre type. This is the least reliable: two cottons can differ a lot depending on construction and finishing.

If you cannot test before buying, buy a little extra, test a corner when it arrives, and cut once you know.

Rounding up at the counter

Shops usually cut in steps, often 10 cm or a quarter or eighth of a yard. Always round the calculated figure up to the next step. Also check that the end of the cut is square: fabric torn or cut off-grain can lose several centimetres at each end once you straighten it, which is another reason to round up.

Projects where it matters most

• Curtains and blinds: long drops multiply small percentages into many centimetres. The guide to curtain fabric works through an example.
• Fitted covers: loose covers, cushion covers and fitted sheets have little room for error.
• Quilts combining fabrics that shrink differently: if some fabrics are pre-washed and others are not, the quilt can pucker unevenly after its first wash.
• Garments in linen, viscose or unsanforised cotton, which can shrink more than you expect.
• Anything lined, where the lining and the outer fabric may shrink by different amounts and pull against each other.

When pre-washing is not possible

Some fabrics should not be pre-washed: dry-clean-only fabrics, fabrics with finishes you want to keep, and many coated or bonded fabrics. If the finished item will never be washed, shrinkage in washing does not matter, but steam pressing and dry cleaning can still cause some shrinkage. For wool suiting, tailors traditionally pre-shrink with steam. For these fabrics, test the cleaning method you will actually use, with care, on an offcut.

If you must cut before washing and the item will be washed later, cut larger using the pre-cut mode. For a single 2.5 m piece of fabric that shrinks 4%, the calculator gives a cut length of 2.6 m.

Dye and colour

Shrinkage is not the only thing a first wash reveals. Strong colours can bleed, especially reds, deep blues and some hand-dyed or batik fabrics. Wash a test piece with a white offcut to see whether the colour runs. If it does, washing the whole length separately before cutting, or choosing a different fabric for a project that mixes colours, saves trouble later.

Pattern repeats, nap and one-way prints

Shrinkage is one reason to buy extra; layout is another, and the two stack. A large printed or woven pattern has to be matched across seams and centred on the item, which wastes part of a repeat for every piece. Fabrics with a nap or pile, such as velvet, corduroy and brushed cotton, and one-way prints, must have every piece cut facing the same direction, so pieces cannot be turned round to nest more tightly. The 15% waste allowance in the example above is a reasonable starting point for plain fabric; for a large repeat or a napped fabric it can be far too low. Lay the pieces out on paper at the fabric's width, or follow the pattern envelope's "with nap" figure, and apply the shrinkage allowance to that larger length, not to the plain-fabric estimate.

A short checklist before you buy

• Area the project needs, including seam allowances and hems.
• Usable width after trimming selvedges, and after width shrinkage.
• Waste allowance suited to the layout: plain, napped, or pattern-matched.
• Length shrinkage from a test or a stated specification.
• Round up to the shop's cutting step, and add a little for squaring the ends.

Write the figures down. If the project goes well, the same numbers will tell you exactly what to buy next time.

What the tools assume

The yardage calculator works from area and usable width with a percentage waste allowance; it does not plan a cutting layout, match patterns, or handle pieces wider than the fabric. The shrinkage calculator applies one percentage to one direction at a time; it does not predict shrinkage, which only a test can tell you. Used together, with your own test result, they give a buying figure you can trust.