A while back, I started a notebook. I write down the fabric, the batting, and the thread used. I measure the quilt top when done piecing, I measure again when done quilting, and one more time after washing and drying the quilt. Yep, quilting shrinks it a bit, and then the washing and drying even more. How much it shrinks does vary. I make mostly full, queen, and a few king sized beds. The loft of the batting even affects the shrinkage from the actual quilting. I usually do not prewash. I think the most I have had a quilt shrink is 6-7 inches and that was a queen flannel quilt. If I had to ballpark it on a queen bed I would say plan on about 3-4 inches but again, that will depend on the fabric, the batting, and the density of the quilting. It has been a good learning tool to keep that notebook.
If you do not want a quilt to shrink much, plan on prewashing your fabric and I would recommend using warm/hot water or whatever you would wash your laundry with. You want your fabric to get the shrinking over with before using it. Same with the drying, I would dry the fabric in the dryer on your normal setting. As for batting shrinkage most batting packaging states how much it will shrink. Remember though, that the actual quilting also decreases the size of the top too. Flannel I would actually consider multiple washings if you do not want much shrinkage.
Last edited by sewingpup; 03-18-2023 at 06:06 PM.