CMinor ... watch when you are in stores for the books that have charts for these things. I have a couple that shows how to do the math, as well as giving you the yardages needed.
eg. one chart is for the HSTs you need for this ... you can look up the size and # needed, and it'll tell you the yardage required. Like MTS, I usually make mine bigger and trim for precision after all the sewing is done, so make sure you calculate accordingly!!
Mine also has charts for the variables of the B .... borders, blocks, binding, backings ... and the yardages required. It;s a great help and I grab it frequently.