Originally Posted by C2H6O
According to Palmer's book you can calculate the AAU's by multiplying the % and weight. So my Galena hops are 10.1% and the recipe calls for 6 AAU's. I plan to add .6 oz. When I plugged these values into beer smith it came out at 1.2 AAU. Can someone explain to me the discrepancy?
Your formula is for HBU's - Home Brew Units.
It was in Joy of Homebrewing, too.
It's a way to compare the relative bitterness of recipes,
but it ignores a lot of variables such as boil gravity and boil time.
Tinseth, Daniels, and Rager formulas are much more complex, and yet each is still only an approximation of actual IBUs.