Thanks very much for you reply. I was thinking of brew house efficiency. Such as 70% of brew house efficiency. I recently purchased Beersmith software and part of determining the grain bill for a recipe is adding in expected brew house efficiency %. I think I've read someplace that there is a calculation to determine this figure from previous brews. Also, (probably more pride than anything else) this calculation let's a brewer know how efficient they were at extracting fermentable sugars from their grain bill. I'm just looking for the lazy brewers way of reaching this calculation. Seems there are calculators to calculate almost anything these days!
I don't have Beersmith so I don't know exactly how they define certain terms.
But from what I understand there are several types of efficiency measured in brewing.
conversion efficiency: where you measure the gravity of the wort after conversion, but before sparging
mash efficiency: using the volume and gravity after the mash and sparge
brew house efficiency: which takes into account all the volume losses till the beer is actually packaged.
Mash efficiency is the one that I think most homebrewers are concerned about because it directly affects recipe formulation.
I suppose brewhouse efficieny is also important but I think most homebrewers just brew a slightly larger batch so they can be sure to get the finished amount of beer into the keg/bottles. I never actually tried to get a number for this.