Originally Posted by Brewnurse
One question, how do I calculate mash efficiency?
Every grain has an associated "ppg" number which tells you the potential gravity points that one pound of that grain could contribute to one gallon of wort. (you can find this on-line).
POUNDS x PPG / GALLONS = theoretical gravity w/ 100% efficiency
Do that calculation for each grain you have and add the numbers up to get your total theoretical gravity.
Now, you can get the efficiency number by doing:
MEASURED_GRAVITY / THEORETICAL_GRAVITY * 100%
..... or.... just use The Recipator, fill in your recipe and tweak the efficiency % until you see an OG that matches what you measured.