I promised that I would provide a free spreadsheet for simultaneously evaluating diminishing returns (via the square root rule) caused by page count and circulation depth within any catalog.
If you wish to play a bit with the simulation tool, please download the free spreadsheet.
The spreadsheet does not have a file forecast component, a very important part of any circulation project. The simulation is not meant to be the "official" plan for any one catalog. Instead, you use the tool to find a good combination of pages/circ-depth, then do the real work via file forecasting and RFM to obtain a circulation plan.