I've seen the calculators and such, but I'm trying to figure out how they come up with the volume they do. I think I understand the first part of wanting to pitch proportionally to the density of sugars and the volume the yeast will be spread through and that the 0.75 constant for ales and 1.5 constant for lagers represents the ideal workload for each cell.
I don't understand how to go from the number of cells you want and the number you have in your packet, to the volume of starter needed. I'm guessing that since your starter gravity is optimized at 1.030 or so, you choose the volume that gives the yeast enough sugar to divide the appropriate number of times and then restock its reserves for dormancy. But how much sugar per cell per division does that take?