The actual cut sizes will depend upon the width of the saw blade used to make the cuts. I usually have the lumber yard cut the 4'x8' sheets into two or three manageable sizes (to fit into the back of my car). Sometimes the "big box" stores charge for more than two cuts and they aren't always as accurate as I hope they could be. But, then, neither am I! :-)
When I do not plan to make "canvas panels" (see below), I put on two or three coats of gesso (usually tinted) on the large pieces when I get them home. I use a foam "rubber" paint rollers to apply the gesso. After the gesso has dried I use a clamped straight edge and a fine-toothed jigsaw or a fine-toothed circular saw to cut the large Masonite panels to the sizes I want. There is some "waste" on two of the drawings but those could be used for small (REALLY small) studies?
Before I apply gesso to the Masonite, and I feel like having some "canvas panels" to paint on, I glue canvas to the panels after they are cut to size. I apply tinted gesso after the glue has dried and the fabric has been trimmed. There are articles on the web that explain the process better than I can. These are the first three I saw after I Googled "how to make canvas panels". There are MANY more articles out there!
I hope this helps somebody cut the cost of their painting supplies.
30 Panels #5
15 each 9"x12"
15 each 12"x16"
WASTE - 3 each 3"x12"
24 Panels #4
24 each 12"x16"
16 each 9"x12"
15 each 12"x16"
9 each 12"x20"
9 each 12"x16"
each 18"x24"WASTE - 2 each 6"x24"