This equation computes the total number of yards of a fabric needed at a specified bolt width.
INPUTS
the total number of blocks you need to cut from the fabric,
the square block width (inches including sewing allowance), and
the width of the fabric bolt.
NOTES
This assumes your blocks are square and that you have already created a combined count of the blocks you'll need to cut from one bolt (single color or pattern) of fabric by combining any pattern shapes that go into those blocks into square blocks.