Why buy more fabric than the pattern says?

Washable fabrics shrink in their first wash. If you buy exactly the pattern amount and pre-wash it, you will end up short. Buying the grossed-up amount means the post-wash yardage matches what your pattern needs.

How is the pre-wash amount calculated?

It divides the required yardage by (1 minus the shrinkage fraction). For 3 yards needed at 5 percent shrinkage, you need 3 divided by 0.95, about 3.16 yards, so the fabric still measures 3 yards after washing.

What shrinkage percentage should I use?

Quilting cotton typically shrinks 2 to 4 percent, flannel and wool 5 to 10 percent, and linen 3 to 5 percent. When the bolt or manufacturer states a figure use that; otherwise pre-wash a test swatch and measure before and after.

Does shrinkage apply to width too?

Yes, fabric usually shrinks in both length and width. This calculator adjusts length yardage, which is what patterns specify. If your layout is width-critical, pre-wash a swatch and check the usable width after washing.

Should I always pre-wash?

Pre-washing is wise whenever the finished item will be laundered, especially for mixed fabrics in one project that may shrink at different rates. Pre-washing each fabric first prevents puckering and distortion after the first wash of the finished piece.

What is the Fabric Shrinkage Calculator?

Enter your pattern yardage requirement and the fabric's expected shrinkage percentage to compute how much fabric to buy before washing, so the pre-shrunk yardage still meets your pattern. For sewers and quilters. It runs free in your browser on Gera Tools, with nothing uploaded.

Fabric Shrinkage Calculator

Name: Fabric Shrinkage Calculator
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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If you pre-wash your fabric, buying exactly the pattern yardage leaves you short because the fabric shrinks before you cut. This calculator grosses up your requirement so that, after washing, the shrunk fabric still meets the pattern.

How it works

Shrinkage removes a percentage of the length, so the amount you must buy is the required amount divided by the fraction that survives washing:

buy = required / (1 − shrinkage%)
lost = buy − required

For example, 3 yards required at 5 percent shrinkage needs 3 / 0.95 ≈ 3.16 yards. Note that you divide rather than simply adding 5 percent: adding 5 percent (3.15 yards) is slightly too little, because the 5 percent loss applies to the larger pre-wash length, not the smaller required length.

Typical shrinkage rates by fabric type

Fabric	Typical shrinkage
Quilting cotton	2–4%
Linen	3–5%
Denim	3–5%
Flannel	5–10%
Wool	5–10%
Rayon / viscose	5–10%
Pre-washed or sanforized	0–1%

These are typical ranges — the actual figure depends on the weave, dye lot, and washing conditions. When in doubt, pre-wash a quarter-yard test swatch, measure it before and after, and use that measured percentage in the calculator.

Worked examples

Example 1 — quilting cotton. A quilt top pattern calls for 2.5 yards. You expect 3% shrinkage.

buy = 2.5 / (1 − 0.03) = 2.5 / 0.97 ≈ 2.58 yards

Round up to 2.75 yards (the next quarter-yard increment at the cutting counter) to be safe.

Example 2 — flannel backing. A lap quilt backing needs 4 yards of wide flannel. Flannel from your store notes 8% shrinkage.

buy = 4 / (1 − 0.08) = 4 / 0.92 ≈ 4.35 yards

Round up to 4.5 yards. That extra 0.5 yards of flannel in the cart easily saves a mid-project trip back to the store.

Example 3 — linen garment. A dress pattern calls for 3 yards of linen and your fabric is labelled 4% shrinkage.

buy = 3 / 0.96 ≈ 3.13 yards → round up to 3.25 yards

Width shrinkage and usable fabric

Most patterns specify length yardage, but fabric can also shrink in width. A fabric that is 44 inches wide before washing might come out of the dryer at 42 or 43 inches. If your pattern layout is tight on width — for instance a large pattern piece that just fits within the bolt width — pre-wash a swatch and measure the finished width. If it has narrowed, you may need to buy extra yardage to account for re-laying the widths-constrained pieces.

When to skip pre-washing

If the finished item will never be laundered (a wall hanging, a sample, display fabric), pre-washing is optional. Some sewers also skip pre-washing fine silks and embroidery fabrics to avoid changing the hand or sheen, opting instead for dry-cleaning care. If you do skip pre-washing, note this in the project for the recipient.

Always round up to the nearest quarter yard at the cutting counter, and pre-wash a test swatch to confirm the manufacturer’s stated shrinkage before committing to a large cut. When several fabrics share one project, pre-wash each separately so they shrink before being sewn together.