Mr. Malty vs. Beersmith Pitching Rate

[ja09]

So this is my first really big beer, a RIS at 1.122. Mr. Malty is telling me I need 423 billion cells and a 4.18L starter, while Beersmith says I will yield 471.3 billion with a 3L starter. Viability is the same in both calculators and both are using a stir plate. These numbers aren't very close to each other.

Is this typical? Which should I go with?

 

[homebrewdad]

It's typical. Yeastcalc.com will also vary from the above two.

Make an educated guess and go with it.

 

[ja09]

Thanks. I ended up doing a 3L starter w/ stir plate because that's the max I can do. After a stupid, stupid, stupid boil over, I probably have ~ 2.7L at 1.041. I'm not totally convinced that's enough for this giant beer. Might pick up another vial and pitch on brew day.