you can get 7 (5") blocks across a yard of fabric- by 8 (5") blocks the width *figuring 40" width* ... so that is 56 (5") blocks per yard of fabric...it of course depends on what size quilt you are making...how many blocks across by how many blocks down the length. once you decide the size of quilt you plan to make then you can figure backing- you could buy *wide* backing fabric- which is anywhere between 90" up to 118" ... 108" is a common wide backing fabric- if you bought 3 yards of 108" fabric you would have 108" x108" which is plenty for a queen sized quilt 6 yards of regular (36" x 40") gives you 108" x 80" if you cut (2) 3 yard pieces & sew them together (minus the seam allowance)