It depends on the bran and company. Medium loft is not always medium loft. The only real way to tell is to buy it and open the package! But in general, I would say medium would be somewhere around 1/4". Hobbs Heirloom Cotton (which is a cotton/poly blend) is a good starting place. Then if you want it loftier, you will have to go to poly batting. If your local Walmart still has crafts, they sell a brand of batting called Polyfil. It comes in several lofts. "Traditional" is very thin. Medium is about 1/4", and high loft is about 1/2". It's a good brand for a low price.