My friend and I are brewing 20 gallon batches in a 30 gal pot and we are missing the mark on our yeast starter. For a 20 gal batch how many starter packs do we need and how much starter wort do we need. Our batches before we have been using on pk of yeast Wyeast and a gallon starter to split among 4- 5 gal carboys. We have beer but it is with diminished ABV. We need a guideline for doing a starter for the 20 gal.
Try using the Mr Malty website, that might give you a good guide.
http://www.mrmalty.com/yeast-tools.php