So for the lager I plan on brewing, Mr.Malty.com suggests 750 billioin yeast cells are needed for a 10 gallon batch. With a stir plate, it suggests 3 vials in about 4.5 liters of wort. 3 vials sets me back 21 bucks. Dropping to two vials and saving $7, requires a starter of 7.7 liters. This is bigger than my biggest flask (5 liters) that would work with my stir plate.

So, the obvious choice is to do a stepped starter. I’m struggling a bit with the math as I read the yeast book. Can someone tell me the best way to arrive at the right number of cells with either using 1 or 2 vials and the flasks that I have (1 liter, 2 liter, and 5 liter)? If it doesn’t work I’ll just bite the bullet and buy the three vials.