The International Bitterness Unit (IBU) provides a measure of the bitterness of beer, which is
derived from the hops doing the boil step. Just like the SRM, the process is a little over the head of the average homebrewer, but thankfully we have programs that will calculate the IBU of a recipe based on the ingredients and methods used. The scale typically ranges from around 2 – 100 IBUs. In addition, the higher the malt bill the higher the IBU has to be for it to be perceived as high. For example, an imperial stout with an IBU of 60 won’t taste as nearly bitter or as hoppy as and india pale ale with an IBT of 50, even though the numbers are similar. If you keep the style in mind, it is very simple to gauge how bitter a beer will be if you know the IBU number and the beer type.
Higher IBU beers have become all the rage as of late, with some companies claim to have well over the 100 IBU threshold. From what I’ve researched, though, is that the human palate cannot detect bitterness over 100 so it seems to be just a waste of hops at that point. Heady Topper, from the Alchemist Brewery in Vermont, is one that comes to mind with an extreme hop bill. I have had the opportunity to taste this on a couple occasions and as someone who only within the past couple years has been able to appreciate hoppy beers this one was way too much for me!
On the flip side, Dogfish Head’s World Wide Stout which packs an incredible 15-20% ABV has an IBU of 70 though it is nowhere near on the same scale of bitterness as something with a smaller IBU such as Troegs HopBack Amber. The Troegs is only at 55 IBU but is much more bitter due to the smaller grainbill used.
Overall, the IBU of a particular brew can tell you a lot about what it is going to taste like, though the best way is to pop the top and enjoy