Originally Posted by
yweinst
so if you pre shrink it, how much more batting do you need to buy than if you do not. I'm assuming that if you buy a twin size for example and wash it, it will be too small to quilt for a twin size top...
You would have to calculate this based on the shrinkage rate of the batting. Most cotton battings shrink around 3% (although they usually say 3-5%). To be safe, you would calculate what your batting length and width would be minus 5% of their pre-wash length and width. Compare the result with your quilt top measurements to see if it will be adequate.