Great question because sizing is art as well as science. In my experience I have found that addressing the largest lists and modules are what will get you closest to the actual size. Here's a template I use below. Oh, and remember... estimate the size of the lists as well as the modules. You'd be surprised how much space lists take. Each list item takes 500 Bytes as overhead + the length of the text! Key point: Don't over analyze. As you can see below the P7 SKU List and any associated module will determine the size of this module. So focus on the biggest lists and the respective modules that use them.