In this post, we discuss International Bittering Units, also known as IBUs. We let Mike talk about what they are and what they are trying to calculate. We also wonder if how much importance they have in today’s beer brewing culture. So, strap in – here’s Mike IBU rant.

What Are IBUs Anyway?

Mike starts off by defining what the unit measures. Each bittering unit is a milligrams per liter of isomerized alpha acids from the hops used in brewing the beer. The creation of this unit of measure is an attempt to quantify the bitterness in beers. It’s nice to have a number for a sense of bitterness but the number depends on calculations of utilization.

The Complication Of The Calculations

As Mike states, it’s taking the number of alpha acid units times the amount of utilization. The first part of that equation, the alpha acid units, is easy to figure out. It’s the amount of hops by weight in your recipe multiplied by the percent of alpha acids (%AA) reported in the hops in your recipe. The utilization part of the equation is not as simple. That part is estimating how quickly the alpha acids in the hops will isomerize and it based on factors like:

  • Weight of Hops Added to the Boil
  • The Amount of Time The Hops Are Boiled
  • The Density of the Wort

Mike says there are other factors that can alter utilization including protein content in the wort, mineral profile of the water, and the true alpha acid percentage of the hops.

So, although it’s nice to have a number, it’s hard to know how helpful that number is.

The Modern Day Brewing Process

With all of the hazy IPAs we’re brewing, we homebrewers still calculate IBUs. Does that make sense? Many times, I don’t add any hops to the boil at all. How can I calculate the IBUs in my beer if the hops haven’t isomerized? Since the utilization of alpha acids is not part of many beers, IBUs can’t be calculated. Therefore, IBUs just aren’t a thing for many beers. Mike rants that they aren’t a thing for hard seltzers either.

Maybe Just Report Alpha Acid Units

With these Brew Dudes recipes, we will make a concerted effort to report out on the alpha acid units (AAU) of our recipes. To us, that makes the most sense for your replication. Even if we don’t have the AAU number for you, you can still calculate it based on the amounts we publish in our recipes.

Hope that helps – let us know what you think of IBUs!

Brew on!