When choosing a beer, International Bitterness Units, or IBUs, are often indicated right below the ABV. While some people may ignore both entirely, and others focus solely on ABV, IBUs are worth noting as an interesting feature to beer that is often overlooked and misunderstood.
Generally speaking, beer ranges from 5 to 120 IBUs. But the human palate generally cannot detect anything over 100. Some less hoppy beers, like lambics and wheat beers, have an IBU of around 10 while IPAs have more iso-alpha acids and can range from 60 to 120 IBUs. An IBU, which is commonly thought of as a measurement of how bitter a beer is, is really just a measurement of how many iso-alpha acids are in the beer. IBUs are technically measured through mass spectrometry, which is an incredibly scientific way of measuring the mass of a specific chemical in a sample mixture. However, most brewers don't send every batch to a lab to test for IBUs, especially small batches. Since iso-alpha acids come from boiling hops, most brewers can estimate the IBU for a specific beer just by knowing factors like what hops they used and how long the hops were boiled.
IBUs can add some confusion for beer drinkers. So, let’s debunk a couple common myths regarding IBUs. First, the IBU of a beer is not the “hoppiness” of a beer, though IBUs and hops are intimately related. Second, just because a beer has a high IBU, it doesn't necessarily mean the beer will taste incredibly bitter.
IBUs are not a level of beer hoppiness. Hoppiness more often than not refers to something known as hop body. Hop body is the flavor of the hops, such as citrus, spice, pine or floral. The hop body is generally what people are seeking when they ask for a hoppy beer. For example, one of my all-time favorite beers, Long Trail's Green Blaze
, has a fantastic pine hop body, but according to the IBU range of an American IPA, it’s on the low end of hop bitterness. Yet, many people I've shared it with have commented on Green Blaze's hoppiness. This is hop body. For more information on hops in general, check out Gotbeer's own Dave Wilfore and his article outlining hops here
Bitterness and IBUs, likewise, don't have a perfect linear relationship. As anyone who has mixed sugar or milk in coffee know, the bitterness of black coffee can easily be cut with a bit of sweetness, which entirely changes the drinking experience. Stouts, for instance, often have higher IBU counts but rarely have the “hoppy bitterness” of an IPA. This is because the malt sweetness of a stout undercuts the bitterness of the iso-alpha acids. This explains why a Green Blaze IPA and a Guinness Stout, which sit near each other on the IBU scale at 60 and 40 respectively, have entirely different levels of bitter taste. Green Blaze is noticeably more bitter than Guinness. It’s what we call perceived bitterness.
Ultimately, one must rely on his or her own palate to determine the bitterness of a beer. As you try more styles, you will be able to narrow in on the IBU range that best complements your taste preference. As always, I'm curious to know what you all think of IBUs. Feel free to let me know your thoughts.