Calculating Hop Weight from AAUs

[holjim]

Forgive me -- I was never very good at math and now it is biting me in the butt...

I am going to hit the LHBS tomorrow to get the goods for BYO Clone's Rogue Hazelnut Brown recipe.

However, unlike almost every other recipe I've seen, it does not list the hops in ounces but rather in AAUs (ie - 7.8 AAUs Perle Hops @ 60 min).

I've tried to follow the directions at BYO's site, which I've calculated out to be 8.5 ounces of Perle but that seems high and I want to make sure I've done the math right.

Two questions:

The obvious one is whether my calculations are right that 7.8 AAUs @ 60 min for a 5 gallon batch with an IBU of 33 will come out to 8.5 ounces.

If so (or if not!), is there an easier way to calculate it other than:

weight of hops in ounces =

IBUs desired x volume of final batch in gallons x 1.34* / alpha acid percent x utilization percent

I should have spent more time studying and less time drinking beer in high school...:cross:

Thanks in advance!

Jim

 

[FlyingHorse]

You're making it harder than it has to be.

AAU (Alpha Acid Unit) = AA% x ounces

1 oz of 10% AA hops = 10 AAU
2 oz of 5% AA hops = 10 AAU
etc.


So the ounces you need = 7.8 AAU / (your Perle hops AA%)

No way it's 8.5 ounces. Perle should be somewhere in the 7-8% AA range, so you're looking at about an ounce

 

[Brewsmith]

AAU= Alpha Acid x Weight in Ounces

You need to know the AA% of your perle hops to figure the amount. Promash is listing them at 8.25%

7.8=8.25 x oz.

oz= 7.8/8.25 = 0.95 oz

If your perle hops are less in AA%, say 7%, the numbers are now 7.8/7 = 1.11 oz

Short answer, divide the AAU by the AA% to get your amount.

 

[Brewsmith]

Perle should be somewhere in the 7-8% AA range, so you're looking at about an ounce

That all you really need right there.

 

[holjim]

Thanks all!