Dry Yeast Cell Counts

I've been looking at the manufacturers websites to try to determine what sort of cell counts can be expected in the dry yeast packets in order to try to work out accurate pitching rates.
Most of them only give a >5 or >6 billion cells per gram etc estimate. I've read on other forums that some yeasts can be around 10-15 billion cells per gram. That's a big difference.
Do any of you guys have more accurate data or know of a better method to work out whats actually in there?

The actual cell count is usually considered 20 billion cells per gram, but that is not what is important as not all those cells will be viable. What maters is how many viable cells end up in your wort. You loose viable yeast cells at a rate of approximately 4% a month assuming they are stored correctly. It is also important to re-hydrate the yeast in water and not just pitch into the wort which can cause the loss of half the cells.

Here is a handy calculator : http://www.mrmalty.com/calc/dry.html - I guess the link does not work as you have to click on terms of use before it works. Just go to Mr Malty yeast page and select the calculator http://www.mrmalty.com/yeast-tools.php

Here is an interesting post about re-hydrating dry yeast: http://seanterrill.com/2011/04/01/dry-yeast-viability/

Ive been using the yeast pitching calculator on the Brewers Friend website however it requires input of the cell count per gram to get an estimate.
I have been using 8b cells per gram rate in my calculations based on what the manufacturers sites state, they only guarantee greater than X amount of cells at time of manufacture and as you say they lose viability over time so I am reluctant to overestimate and go with 20 billion when they can only guarantee about a 3rd of that when the packet leaves the factory.
I guess its always safer to over pitch than under pitch?

I had a look at the Brewers Friend calculator and using the defaults it tells me I need 35 grams of dry yeast for my 1.069 IPA. Mr Malty says 16 grams. In my experience Mr Malty is more correct and 35 grams seems absurd, but I have not used dry yeast now for quite a few years.

TAHammerton said:

I had a look at the Brewers Friend calculator and using the defaults it tells me I need 35 grams of dry yeast for my 1.069 IPA. Mr Malty says 16 grams. In my experience Mr Malty is more correct and 35 grams seems absurd, but I have not used dry yeast now for quite a few years.

Click to expand...

Yeah, 35 grams is wild.
There's a thread on the AHA forum that got pretty intense and lost me, but a bottom line for dummies is that these calculators overstate how much yeast needs to be used... best advice (again, for dummies like me) is to take good notes and tweak things over time per your own experience.

https://www.homebrewersassociation.org/forum/index.php?topic=24447.0