AAU Calc. vs Beer Smith AAU Calc.

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?

C2H6O said:

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?

Click to expand...

Different boil times/gravities. What do you have set for the boil volume and time? A 60 minute boil would give you much more IBUs than a 5 minute boil, for example, and a higher SG wort will give you less utilization.

Total batch size is 5 gal. Initial boil is 2 gal for 60 minutes. The OG = 1.045.

I think you have your AAU's confused with your hop utilization, or what it contributes to your IBU's (this is what I believe BeerSmith is showing you). Check out How to Brew again, Chapter 5 section 4 here: How to Brew - By John Palmer - Hop Measurement. This might clear it up for you.

C2H6O said:

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?

Click to expand...

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.

All - Thanks for the replies.