So I have found some off flavors in a few of my beers that I haven't been the happiest with. I believe a few issues are to blame, but I think I have been under pitching dry yeast. After taking Lee's advice on brewersfriend.com (really starting to like it). They have a yeast calc there and with some data to back it up.
Here is a link to the calc with a blonde ale I'm contemplating:
http://www.brewersfriend.com/yeast-pitc ... sttype=dry
I'm using the probrewer .75 pitch rate, which is mentioned on many different articles and appears to be generally accepted as a conservative number for normal ales.
Scroll down to the Dry Yeast explanation and MrMalty, claims 20B cells per gram for dry yeast in their calc. HOWEVER, if you go look on fermentis website and look at the details for us-05, they clearly state:
Viable cell at packaging: 6 x 10^9/G (6B cells per gram)
Using the yeast pitch rate forumla provided on MrMalty for an ale:
(0.75 million) X (milliliters of wort) X (degrees Plato of the wort)
This will tell us how many billion cells of yeast we need for our specific beer (same thing the calc does).
There are about 3785 milliliters in a gallon
Doing the math on my batch of 6 gallons in the fermenter and an OG of 1.042 (about 10.3 Plato):
(750,000) X (22,710) X (10.3) = 175,434,750,000.
Or about 175.5 Billion cells!
Using Fermentis own numbers of 6B cells a gram we would need:
175.5 / 6 = 29.25 grams of US-05 to meet these standards.
That is almost 3X more than what most of us probably do.
-Martin