Newbie here so be gentle. I have a whole grain recipe to replicate Sierra Pale Ale that calls for Bittering Hops of 1 oz of Cascade at 5.7 AAU and Flavoring Hops of 3oz Cascade at 4.9 AAU.
Here’s the dumb question: wouldn’t Cascade Hops all have roughly the same AAU or is there some way I adjust this? Or is this the wrong question altogether? What do I need to know here?
Different crops from different locations can have different characteristics. Terroir plays into it, just like with wine. To make subs, multiply the AA by the weight to get HBU (homebrew bittering units). For instance, one oz. of 5% AA hops is equivalent in bittering to 2 oz. of 2.5% AA hops. You can ust that for any hops added before about 20 min, to end of boil. From that point on to the end of boil, you get mainly flavor and aroma and very little to no bittering. For addition 20 min. or under, go by weight.
That’s a bit odd, but my guess is that the person who wrote the recipe had bags from two different crops/years/sources and they varied a bit. Denny’s answer is correct, but we all knew that didn’t we? 
It’s from the recipes in the back of “Homebrewing for Dummies” by Marty Nachel. I’m not a big fan of the “Dummies” series, but the recipe looked interesting.
If you want way too much feedback on it feel free to post it here!
Check pout the AHA recipe wiki, too.
Thank you, Denny. That recipe index is a nice reference.
I think I figger’d out my original question. Correct me if I’m wrong.
On a package of any given hop, (hops??) there should be an AAU number. So if a recipe calls for 8 AAU and the hop package states an AAU content of 6, you’d want to go with 1-1/3 oz of that particular hop. (1 oz gives you 6 AAU and 1/3 of 6 is 2, so add it to 6 to get the neede 8 AAU) So the AAU is stated on a recipe to adjust for seasonal variations in AAU.
Am I gettin’ this or what?
Close,
the package will likely tell you the AA (Alpha Acid) percentage. The calculation to determine AAU is AA% times ounces. so if you have a package of cascade hops labels as 8.9% AA and you add 1 ounce at 60 minutes you have added 8.9 AAU.
this is very rough but gets you close to the level of bitterness you can expect the finished product. once you are good and hooked you can learn about some more complex calculations or get some software to do the math for you.
This is almost as much fun as hand-loading.
I am sure that means something different than what I think it means. 8)
I’ll take “squeezing off a round” for $100, Alex :o