In order to work out the amount of fabric you need a pattern.
The chevrons measure length and width ,how many using either l or w fit into 40 inches. The other measurement is amount .ie chevron 21/2 inch by 5inh. Using 21/2" means go into 40" by 16. Now requirements 5" down one row of cuts.
Then work out for your quilt.
Hope you understand. Work each shape at a time and then add them all together.