making 100 billion cells from?

I was going to divide some smack-packs/vials into test tubes (autoclaved equipment), and then step up these tubes when I need them. I was thinking of dividing 4 or 5 ways, and then using 500mL as a first step up, and then going from there. How can I extract information from pitching calculators to figure out smaller amounts of yeast growth?

Should I divide more/less, and/or use larger/smaller first-step starters? I'll be using a stir-plate with an initial heavy blast of O2.

The goal is to have 100 billion cells, so I can go from there as I am used to doing.

I've been looking at the charts in 'Yeast' and the mrmalty calculator, and confusing myself. Any hints/suggestions? I would love to be able to count cells, but don't have a scope or haeceomter (sp?).

Cheers/Thanks

Keep with the Yeast book. Everything you need to know is in there. Yeast population dynamics are complex and as yet still fairly poorly researched. I prefer the Wyeast calculator to the Mr. Malty calculator. Both produce nearly identical final results, but I find the Wyeast calc to give me closer access to the numbers. You can always tell the calculators that you are using fractions of a packet to accomplish what you are talking about. In any case, without a haemocytometer, you'll be dealing with relatively crude approximations, but that is okay.

I've never found the O2 to be necessary on a stir plate, but I don't think you'll hurt anything with it.

You can build up from as small of a population as you like, but the smaller you go the more important good sanitation becomes.

500mL seems like a reasonable first step for a 25B cell starter chain, but if you were going to be storing the yeast for a while I'd consider starting at more like 250mL. There wouldn't be as much growth in a 250mL starter, but it would give your yeast a chance to restock glycogen reserves, etc.