I often use the same fabric for an inner border as the binding, and if I have enough, I do cut lengthwise so I don't have to piece the borders. But you can do it whichever way you want. I've found that many of the people at Joann's don't have a clue. For future reference, here is a binding calculator to help you figure what you need before you go:
http://www.quiltersparadiseesc.com/C...Calculator.php