I think I read 3%? And I have found that the less expensive fabric (walmart, cheaper lines from joann's, etc) do shrink more than the more spendy brands.

MODA should not shrink. I never prewash my cottons. Flannels are a different story. You must prewash those.

Better quality cottons generally shrink by maximum of 3% and poorer quality can be up to 10%. I don't was any of my fabric and the shrinkage is negligible.

How does one wash batting? I thought it would come apart if washed?

I read something somewhere recently that on average shrinking is about 2% in fabrics. I'm sure poor quality fabrics are more. I think you will be ok. I would just not wash it. Use it like it is. Then you will have some nice use out of it. When it finally does need a washing you can go ahead and give it a shot and wash it. If it does shrink some you will at least have got some good use out of it in the correct size.

Wolfkitty, it would depend on the batting. I haven't had any problems with all the name brand batting out there.. just put it in the washer and run it. Most of them should have directions on the packaging.

Thank you for your reply, mailmanldy!

batting packaging have instructions for pre-shrinking your batting if you feel you need to...it also tells you how much it will shrink. everyone really needs to get in the habit of reading their packaging it contains a wealth of valuable information.
looser weave fabrics shrink more than tight weave fabrics...so homespuns will shrink ALOT compared to moda cottons, which will shrink more than batiks.
if shrinkage is a concern you should always pre-wash your fabrics. i have never pre-washed my batting, i just make sure i purchase the batting that is going to behave the way i want it to...such as only shrinking an inch or two...

I wash fabric and batting and never have a problem.

How do you wash the batting?