Originally Posted by passedpawn
1 million per ml per °Plato. Maybe less for ales, more for lagers, but that is the number I shoot for.
Unless you mean for your target beer - I'll have to disagree. While this is perfect target for fermenting wort, growing yeast cells needs a much higher pitching rate. So we don't get confused, I'll call the starter pitch rate the "inoculation rate"
For the starter, you want a inoculation rate in the ball park of 5-15 million cells per ml / degree Plato.
For example, in a 1.5 liter starter of 1.036 gravity with a Wyeast pack of 100 billion cells gives you an inoculation rate of:
total cells = inoc rate * mls wort * plato
100 billion = (X) * 1500 mls * 9 Plato
(X) = 7.4 million cells per ml/plato
This will give you a decent yield in the starter.