Originally Posted by borntobrew
The simple answer is comparing your specific gravity with what is the potential sg for the volume you have. Palmer's book "How to Brew" will help with figuring your potential. But one thing I don't know that maybe someone can answer is what sg do you measure. When I measure the sg of preboil wort I get a higher efficiency than if I measure the post boil wort. Since efficiency is a function of the mash, I figure the numbers should be the same. Anybody know what I'm missing?
You can calculate efficiency at several steps along the way. It will provide different information. For example if you want to know how efficient your mash process/equipement is you measure your pre-boil volume and SG and calculate that. This is most usefull when dialing in your mash/sparge process. If you want to know your "Brewhouse" efficiency you would calculate that based on the volume of wort you place in your fermentor and its SG - this will tell you how efficient your whole
process is. Your brewhouse efficiency will always be less then your mash efficiency - the difference between the two will reflect your losses during the boiling, cooling and transfer process