For the border, first decide how big of a border you want. I would do 5", but I like big borders. So I'm going to do this with 5.5" (unfinished) and then just change the 5.5" if you do something else.
Assuming it's 63.5x63.5 for the quilt, you want a border on all 4 sides, right? :) So imagine (draw a picture if it will help), that you add 2 borders, on the left and right side of the quilt. They would need to be 63.5" each to cover the whole side, right? So you need 2 pieces of fabric 5.5" x 63.5".
So now for the top and bottom, you need 63" (that's now just 63 because the seam allowance is sewn) PLUS 5.5" on the left and 5.5" on the right = 74". So you need 2 pieces that are 5.5" x 74" (you'll probably have .25 or .5 extra, but that's minor).
So if you line those up, end to end, you have a reeeealy big piece that is 5.5" x (74x2 + 63.5x2) = 5.5" x 275". Divide by 40" in each piece of fabric, you get 7 (rounded) 5.5" strips of fabric. So you want to get 38.5". Round up.
Backing (very rough since I have to get going :shock: ). Quilt is now 74x74 (more or less). Get 4.5 yards.