How to accurately calculate mash efficiency?

[M_norrick]

I have always used beercalculus for all of my brew sessions. Seems like my og comes in high everytime. Does anyone know the easiest and most accurate way to calculate the effiency?

Thanks in advance!

[BREWsmith]

Of course the easiest way is to plug your original gravity into Beersmith, Promash or one of the numerous free web sites such as Hopville.com. For a simple back of the napkin approach I take my post-boil gravity points (1.058 = 58 gravity points) times the post-boil volume divided by the pounds of grain times a constant of 36 representing the average potential gravity points in a pound of grain. So, if I produced 6 gallons post-boil with a 1.058 OG from 13 pounds of grain by formula would be:

(58 x 6) / (36 x 13) = 348 / 468 = 74.4% effeciency

Also, if you're adding sugar, the gravity points for sugar is 46, so add that to the total potential gravity points of your grain in the denominator.

If you want to be really precise you can figure out the potential gravity points from each type of grain instead of using a constant of 36. Life's too short...

[psfred]

You should be able to back calculate the difference in what you get and the assumed efficiency in beercalculus -- I'm sure it's in there somewhere. You should also be able to change it

I use BeerAlchemy, which is nice if you have a Mac. It's set up to use 75% or so by default, but I never get less than 80% unless I'm using old malt or something else goes wrong. My usualy efficiency is 80%, its sometimes as high as 83%, but I do a slow fly sparge in a narrow bucket. I had to change it to get the correct final gravity.

Peter