So I brewed the book "Beer Captured"'s Fat Tire Clone the other day. I made a few slight variations. One being I used Wyeast 1056 instead of a Belgian Yeast because I figured since it's not a Belgian Ale why use a Belgian yeast (I also contacted New Belgium Brewery and the confirmed my theory and said I was on the right track)

My other change though was that it calls for .33oz of Magnum Hops (14%AA) The Magnum hops I had were only 12.5%AA, so I was going to bump it up to .66oz and the IBUs would come out at 26.4. (The book said IBU of 21). I had 1oz of Magnum, and I'm kind of a hophead, so I ended up bumping it up to .75oz which put the IBUs around 30.

My other hop additions are a .5oz Hallertauer (4.3%AA) at 15mins and .25oz Willamette (4%AA) at flameout.

Now I haven't really experimented too much with changing recipes. I mostly stick to the book. But, now I'm thinking should I have bumped up the other hops as well? With the higher amount of Alpha Acids from the Magnums, will the bitterness overpower any hop aroma from the late additions since they weren't increased at all? I know I'll just have to wait and see, but my question is if I increase the bittering hops in a recipe, should you also increase your flavor/aroma hops as well to help balance it out?

3 Answers 3


Fat Tire isn't Belgian-y at all, and 1056 is probably a nice sub. It's been a while since I had it, but it's yeastier than 1056 - less yeasty than a Belgian by a long shot though. Probably some American Ale hybrid (like Denny's Favorite) would be a good choice, but you can never really go wrong with good ole 1056.

A third of an ounce of hops isn't going to move the needle a ton, really. And, you're getting very little AAs from those late editions - nearly none in the flameout one (you'll likely extract SOME because inevitably, you can't immediately cool, but not enough to matter). The 15 minute addition will only be slightly more.

Fundamentally, modifying those late hop additions is about what you want in the beer. Do you want hoppy flavors/aromas? More late additions. If you just want more bitter - more long boil additions. But for the largest part, those two variables are moveable based on taste more than anything.


The alpha acid content of hops when added at 15- and 0-minutes don't really matter that much. It's not the alpha acids you're worried about at that point, it's the hop oils.

The difference between 30 and 21 IBUs is inconsequential. Most people can't discern a difference of 5 IBUs or less. And the IBUs calculated by you (and by the recipe you followed) probably used one of the two main IBU estimation formulas (Rager and Tinseth), which are not exactly super accurate. Predicting IBUs includes so many variables -- many of which aren't even understood. All you can do is try to be consistent and you'll end up with somewhat consistent results.

Frequently you'll buy hops that have a different AA % than what is called for in the recipe. It's easy to adjust. For example, your recipe called for .33oz @ 14%AA, but the hops you had were 12.5%AA. To figure out how much you should use,

(recipe amount * recipe AA) / (actual AA) = actual amount

or, in your case:

(.33 * .14) / .125 = .37oz
  • I didn't think hops scaled linearly like you are outlining. The difference is trivial probably if I calculated it out, but the final IBUs may be different if you compare a dilution calculation to an isomerization/IBU calculation at the two different AA and weights.
    – brewchez
    Mar 28, 2012 at 23:26
  • I don't know that it's exactly linear, but it's close. Bascially you're converting the recipe hops into homebrew bitterness units (beertoolspro.com/wiki/Homebrew_Bitterness_Units) and then scaling as needed.
    – Hopwise
    Mar 29, 2012 at 2:00
  • That isn't scaling at all, it is just compensating to achieve the same total AA addition and same IBU. Changing the total AA addition to change IBU would be scaling; and for a fixed OG and fixed boiling time(and altitude) AA-IBU scales very linear due to the very high dilutions involved. (an IBU is basically PPM isomerized AA) However the bitter taste does not scale linear with IBU, and IBU says nothing about the bitterness profile(which changes mostly with cultivar of hops and maybe storage methods). And again this is all assuming the same base wort, apples to apples.
    – Max Power
    Aug 20, 2020 at 3:17

Bittering hops don't really effect aroma additions significantly so I wouldn't worry about it.

Coupled with the fact that a quarter ounce of a 4%AA hop isn't going to be noticable at all as an aroma addition. Same goes for the 15min addition too.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.