Cotton shrinks when you wash it. That part isn't controversial. The question is whether YOU should pre-wash before sewing, or just deal with shrinkage later. Here's the call.
How much does cotton actually shrink?
Depends on the fabric:
- Cotton jersey, French terry, fleece — 5–10% shrinkage on first wash. Sometimes more if it's a heavy gauge.
- Cotton woven (denim, twill, canvas) — 3–7%.
- Pre-shrunk / sanforized cotton — 1–3%. Already done at the mill. Most decent denim sold in the US is sanforized.
- Raw / unsanforized denim — can shrink 8–10%+. Buyer beware.
5% on a yard of fabric = about 1.8 inches. Enough to ruin a fit if you don't account for it.
Should you pre-wash?
Pre-wash if:
- You're making clothes that need to fit precisely (jeans, fitted tees, dresses)
- You're combining fabrics with different shrinkage rates (e.g. cotton lining + cotton outer)
- You bought raw or unsanforized denim — you HAVE to soak it before cutting
- You want to lock in the look before sewing (some cottons soften noticeably after one wash)
Skip pre-wash if:
- You're making bags, home decor, quilts — shrinkage either doesn't matter or adds character
- You're working with already-sanforized fabric and the project has wiggle room
- You want that "one wash" puckered look on selvedge denim (intentional shrink-to-fit)
How to pre-wash
Wash + dry the fabric the same way the finished garment will be washed. If you're going to wash on warm and tumble dry — pre-wash on warm and tumble dry. The fabric will shrink to whatever conditions you set.
For raw denim — cold soak for 30 min, then hang dry. Don't agitate it (you'll mess up the indigo).
The honest answer
If you're making something that needs to fit, pre-wash. The 30 minutes you save by skipping it isn't worth re-cutting fabric.
If you're a beginner — just pre-wash everything for the first year. Build the habit.
What we sell
Most of our cotton is pre-shrunk at the mill (we'll note it on the product page). The denim is split — sanforized for everyday use, plus raw selvedge for the heads who want to break it in themselves.
Got a question about a specific bolt? Email contact@kbmfabrics.store — we'll tell you straight up if it's pre-shrunk or not.