The ABCs of IBUs

Why a big number doesn’t tell you anything about beer

Pints by Jason Foster

illustration by Myron Campbell

I’ve been heartened and impressed at the rapid growth in consumers’ beer knowledge over the past couple of years. People really are starting to understand what craft beer is about — so much so that I find concepts and terms that were the solitary purview of beer geeks just a few short years ago are entering the general vernacular.

Case in point: IBUs.

IBU is the acronym for international bittering units — the standard for measuring the amount of bitterness in a beer. It was created by scientists in the 1960s for quality control purposes, to find a way to consistently measure bitterness in beer — and for most of its history was restricted to brewery laboratories (you can only accurately measure IBUs through lab tests).

Over the past two or three decades, homebrewers picked it up to help them add more finesse to their home creations. It was always treated as a strictly technical measure, though: something to help with recipe formulation and quality control.

More recently hopheads have embraced the term to help them seek out increasingly hoppier beer — and that’s where things took a turn for the worse. Today I find those three letters everywhere: on bottle labels, in ads, on beer bar menus, and, increasingly, on the lips of beer-curious consumers.

I have mixed feelings about this turn of events. On one hand, I’m thrilled consumers are learning about the technical details of beer and integrating it into their appreciation of it.

However, the term is also being misused and misunderstood. And that frustrates me. Allow me to explain.

IBU is a calculated number that represents the amount of alpha acids (the bittering agent found in hops) that have absorbed into the beer. A standard North American pale lager might run 10-15 IBUs. An American Pale Ale will hit about 40-50, while a hoppy India Pale Ale will hit 70 or so. The biggest, hoppiest beer will close in on 100 IBUs.

Sounds simple, except it’s not. It is far more complicated than that — and that’s why the term is being misunderstood. People are under the misguided impression that knowing the IBU number actually tells you something meaningful about the beer.

It doesn’t. Here’s why.

First, there’s no context to the number. The label might say the beer is 40 IBUs. Okay. What exactly does that mean to me? Is that a lot? Is it low? What will it mean for what I taste? The number on its own is not useful.

Second: the number being provided is almost always what we call “calculated” IBUs, which is the number before brewing. Actual IBUs can only be measured in a laboratory after the fact — and there can be a big difference between calculated and actual, because the science behind bitterness extraction is very complex. There are many factors that will affect how bitter the beer becomes, including the alcohol strength, the types of acids found in the hop, and even the size and shape of the brew kettle. What you get might actually be quite different than what the label says.

But most importantly, bitterness is only one flavour component of beer — our perception of bitter is also affected by the other ingredients. Sweetness from malt counters our perception of bitterness, so increasing the malt character of a beer will make it seem less bitter even if the total number of IBUs remains unchanged.

Let me clarify with an example. American Pale Ales are noted for being bitter and hop-forward. They typically have between 40 and 50 IBUs. Sounds good. Now take a wild guess how many IBUs are found in an inky black, heavy Irish Stout, which has almost no hop presence and is all about the malt? That’s right — 40-50 IBUs. All that extra malt body and sweetness in the stout needs more hops just to keep the beer in balance.

The race for more IBUs is getting ludicrous. A couple years ago I tried a beer that claimed to be a world-record 1200 IBUs. Sounds impressive, no? No. Here is the rub. Practical issues mean that bitterness has a ceiling of about 150 IBUs. Higher than that is not possible. Worse, the human palate has a natural limit; we can only perceive up to about 100-120 IBUs. Anything more goes undetected. Trying to cram 1200 IBUs in is just a waste of hops and money.

Rattling off the IBU number in isolation tells you almost nothing about the beer, unless it’s accompanied by other details such as style, colour, alcohol strength, and so on. IBUs only tell part of the story, and a fairly small part at that.

Go ahead, beer drinkers, embrace terms like IBU. Just make sure you have a full understanding of what exactly it means for what you are tasting.