You might consider drawing out the shapes you need (including seam allowances) on graph paper - and then count how many pieces you will need. Remember to allow for how you plan to lay out the pieces (grainlines). I would "assume" that a "yard of usable fabric" would equal approximately (36 x 40) square inches.
That's a bit tedious - but might work if you want to cut it close.
I would probably buy at least four yards. But- when I can - I would rather have a half yard left over than be two inches short. I also tend to make cutting errors or change my mind - so I sometimes have "waste". I also wash fabrics before cutting. Batiks usually have less shrinkage than other "quilting cottons" - but I am firmly entrenched in the "I want to wash the fabric before I cut it" camp.
I also usually cut so that the grainlines of the pieces will be perpendicular and parallel with the outside edges. Some people say grainlines do not matter when making a quilt - they do to me. That also tends to use more fabric than just laying out the pieces "however".
There will be more/other opinions.
Just a note/reminder - that the smaller the pieces - the more that gets "used up" in seam allowances.
Examples:
A "finished" 8 inch square is cut at 8.5 square inches.
72.25 - 64 = 8.25 inches of that square will be hidden in the back in a seam allowance.
11.4 % of the cut square will go into the seam allowances.
A "finished" 1 inch square will be cut at 1.5 inches
2.25 cut size (square inches) - 1 inch finished size = 1.25 square inches goes into the seam allowances and is om the back
So - the seam allowances take up more than 55 percent of the total cut square.