What is a Fat Quarter? Fat Quarters are cut as a 1/2 yard from the bolt and then cut again at the fold. This makes each piece a Fat Quarter which is approximately 18" x 20" to 24" depending on the width of the fabric. Fat quarters are nice to use for scrappy and fat quarter quilts. They are also great for building up your fabric stash. All Fat quarters are 100% cotton unless otherwise noted in the description.