IBU: Most of us know the acronym, but what is it really measuring?

Ode, to the joy that is bitter beer! For all of you out there that share in the love of a good, hopped up ale, this article is yours.
IBU’s, the measurement that all hop-heads look to on every brew they even consider imbibing in, to validate the finding of yet another floral & pungent beer. We’ve all seen beers such as Lagunitas’ Hop Stoopid, that proclaim copious amounts of that wonderful quality, IBU’s, and in this beer’s case, we’re talking 102. Excellent, right?! But what does that really tell you. Ok, your now thinking something like…”well that’s obvious, it’s telling me that damn, this is going to be bitter!”, and you’d be right…….right?
Well, actually, only partly correct. IBU stands for International Bitterness Unit, which tends to indicate the level of bitterness of any particular brew. But oh baby, it is much more than that. According to Zymipedia, the IBU measurement of a brew “reflects the amount of isomerized alpha acids in the final product”. You’ll typically find the level of alpha acid on the package of the hop varietal you purchased. Over all, though, the IBU measurement is one piece of what you & I consider a beers’ bitterness. Duration of the boil, gravity (amongst others), actually depicit the end bitterness much more effectively.
To geek out a bit, here is one of the widely accepted formula’s to calculate your beer’s IBU rating:

, where

• W refers to the weight of the hops used,
• A refers to the alpha acid percentage, which is influenced by many factors, including cultivation method, species, and time of year — hops are often sold labeled with this percentage
• U is the percentage of alpha acid that is actually used during the boiling process
• V means the volume of the wort,
• K is a constant factor that adjusts the measurement to account for the units used.

All in all, bitterness & IBU’s are used interchangeably these days. If you like it bitter, keep your eyes peeled for a higher IBU rating. Enjoy those wonderful hop flavors!

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