Yesterday went to Joann's especially for the sale on the quilting calculator plus 10% off. It is fabulous. I played with it all morning. (Couldn't sleep, the time change affects me). In the past, I have either bought way too much fabric (stash builder), or not enough fabric for a project. I can really use this, and it is very easy to figure out. Even has a quick guide storage in the back of the calculator.
You can get yardage for sashing, for blocks, for backing, for binding. This would be a very useful item on your Holiday list. Wish it had a calculation for jelly rolls, layer cakes too.