Short answer: if the finished project will be washed, wash the fabric first. Prewashing removes shrinkage, excess dye and the sizing chemicals that make new fabric stiff, so your project keeps its shape after its first trip through the laundry.
Why prewash?
- Shrinkage. Cotton can shrink 3–5% and flannel even more — enough to ruin a fitted garment.
- Dye bleeding. Bright reds and dark indigos can stain lighter fabrics sewn next to them.
- Chemicals and sizing. New fabric is treated with finishes that some people find irritating.
Typical shrinkage by fabric
| Fabric | Typical shrinkage | Prewash? |
|---|---|---|
| Quilting cotton | 2–5% | Yes for clothes; optional for quilts |
| Flannel | 5–10% | Always, ideally twice |
| Linen | 3–6% | Yes |
| Rayon | 3–8% | Yes, cool and gentle |
| Denim (non-stretch) | 3–5% | Yes |
| Polyester and fleece | <1% | Not needed |
| Wool | Can felt | Steam or dry clean method |
The yardage calculator lets you add a shrinkage percentage so you buy enough.
How to prewash fabric
- Finish the cut edges. Zigzag, serge or snip the corners diagonally to reduce fraying.
- Wash as you'll wash the finished item. Same temperature, same detergent.
- Add a color catcher sheet for reds, darks and batiks.
- Dry as you'll dry the finished item. If it'll be tumble dried later, tumble dry now.
- Press while slightly damp and fold for storage or cutting.
Tap a step when it's done.
When you can skip it
- Projects that will never be washed (wall hangings, framed fabric art).
- Pre-cuts like charm packs and jelly rolls — washing distorts the small pieces.
- Polyester, fleece and felt-based crafts.
- Quilters who like the crinkly look of shrinkage after the first wash.
Not sure? Cut a 4" square, measure it, wash and dry it, then measure again. You'll know exactly how much the fabric shrinks.
Frequently asked questions
Do I need to prewash fabric before sewing?
Yes, if the finished item will be washed. Prewashing removes shrinkage and excess dye. You can skip it for polyester, fleece, pre-cuts and projects that won't be washed.
How do you prewash fabric without fraying?
Zigzag or serge the cut edges, or trim them with pinking shears, before washing. Snipping the corners diagonally also helps.
Does fleece shrink?
Polyester fleece shrinks less than 1%, so it generally doesn't need to be prewashed.
