Dear sunkistmi:
There really is no pattern. It all depends on the size of your shelves.
My book shelf measured:12" deep x 40" long.
I wanted 3 "stacks" per shelf with a little "wiggle room" between the stacks. The cardboard dimensions I used were: 11" x 12".
The cardboard doesn't have to be thick. Most of mine were from
cereal boxes and soft drink cartons.
I've recycled a few of my many plastic boxes to store seam binding, bias tape, trims, etc. The rest found homes as containers for off season clothing and shoes.
Good luck!
Marveen in Sunny Tucson
Marveen
in Sunny Tucson