What Is IBU in Beer? (International Bitterness Units)

By Matt Richmond

Imagine if someone was able to measure how bitter you were after getting picked last in adult kickball. The measurement would be embarrassingly high, right? Well, good thing you’re a human being because IBU measures bitterness, but only in beer.

Specifically, IBU is the International Bittering Units scale. IBU and ABV (Alcohol By Volume) are the most common measurements of a beer’s contents used by the beer industry to describe their products.

The funny thing is that even many avid beer drinkers can’t explain the significance of a beer’s IBU. Is a high IBU count indicative of a quality imperial IPA? How about an imperial stout? Or amber ales? What number of IBUs should convince you to pour all the beers down your gullet? (For me, any number will do.)

So all bitterness aside, let me brew up a tall, cold glass of truth about why the bitterness of a beer is measured, how it began, how it’s used in the brewing process to complete finished beer, and how to understand the typical IBU range and their differences among various beer styles.

Why Do We Even Need to Know a Beer’s Bitterness?

When discussing the term IBU, what we’re really talking about is what exactly makes beer attain the flavor of beer. The bitterness of the beer creates a balance among all the ingredients, so IBU levels function as a kind of quality control tool.

Malt produces varieties of sweetness. Hop bitterness is the yin to malt’s sweet yang to complete that taste for which beer lovers yearn. Brewers pay attention to hop utilization to balance that flavor so your taste buds can dance in delight at every sip.

How bittersweet.

small glass of dark beer on wood table with rustic brown background

Unlike the experience of attending your best friend’s wedding while single, bringing bitterness to balance things out is a good thing people want.

That being said, breweries make beer by using a chemical process. Understanding the general science behind each step of the process enables brewers to accurately yield the results they want.

What Exactly Makes Beer Bitter and How Do You Calculate That?

To use the bitterness level in beer as a unit of measurement, what aspects of the beer are tested and calculated?

One particular chemical compound gives beer bitterness. Isohumulone is the acid found in hops, so IBU measures the parts per million of Isohumulone. If you want to get really specific, isomerized and oxidized alpha acids and polyphenols make up the bitter compounds in a brew. (Try saying that 5 times after a few cold ones!)

That doesn’t mean that these chemicals are the only reason bitter beers taste this way. There are other processes and ingredients that are used by brewers to bitter up a type of beer. Certain spices, herbs or black malts might be the reason your face puckered up after that last sip.

Bitterness is not the same as hoppiness (or happiness)

I have to note that bitterness is not the same as hoppiness. Not happiness, mind you, though for many they’re one and the same. I’m talking about hop additions to beer production.

When hops are added early in the process, the end result can taste bitter. But added later, the finished product will taste and smelly hoppy. Therefore, even with a lower IBU, you’re getting that bitter hop flavor in the beer.

While it’s not an exact science, a brewer checks the alpha acid content of the hops used and makes an educated guess. What is then calculated is the volume of hops and the conversion rate of the alpha acids in the kettle.

There are a few other ways that the world of craft beer uses to check IBUs as well, which we’ll get to later when talking the IBU “origin story.”

So Are There “Good” IBU Counts?

The range of the IBU scale starts at zero and pretty much to infinity, but most beers stay within the 0 to 100 range. The human palate can only really detect up to about 110 measured IBU anyway. Achieving a higher IBU than that would make no difference to the drinking experience.

Even so, our perception of bitterness is all about the balance of ingredients and the fermentation process of the beer. So high IBUs may indicate that the beer tastes a certain way, but this doesn’t take into account the aforementioned balancing act.

For example, a Double IPA typically has higher alcohol content and is on the bitter side. To get a higher IBU, it needs to be complemented well with sweetness to achieve this lovely recipe.

2 men and 2 women drinking beer and smiling around a bar table

It’s also worth noting that the sensory bitterness of beer isn’t for everyone. Beers that test high on the International Bitterness Units scale might taste absolutely disgusting to one and delicious to the next. So there’s a practical reason this code displays on bottles for the consumer to see. It gives them an idea of whether they’ll like it before buying it.

Still, it’s good to be adventurous! A beer with high IBU doesn’t necessarily mean it’ll be too bitter for your particular tastes. But once you discover what you like in a particular kind of beer, you’ll know what to keep buying or find inspiration in a new libation to enjoy next.

The Heroic Origin Story of the IBU Rating

Old Timey scientist with vials and scales measuring liquids in black and white

Beginning in the early 20th century, the degree of bitterness became possible to test during the brewing process. At first, the methods used were either inaccurate, would take too long, or both.

For example, in 1955 chloroform was used to extract the bitter substance. Then the dried extract would be weighed. This turned out to be an ineffective method because it didn’t take into account other substances that needed to be extracted.

To improve accuracy, this method was developed by taking the iso-octane extract of the acidified beer and washing it with acidified methanol. This removed impurities, calculating results as iso-humulones using ultraviolet light and becoming the industry standard. There was still room for improvement, however, since this process needed to be faster to be the most useful for brewers.

Another method came along using a higher ultraviolet wavelength to skip the washing process, but then there were two competing methods to measure bittering compounds.

In 1964, the American Society of Brewing Chemists (ASBC) tested the accuracy of each method to make the determination for which would become the industry standard. While both pretty accurate, the Rigby and Bethune method of washing the iso-octane extract and using ultraviolet light won out. The organization announced that this method would now be called International Bitterness Units.

lab setting with spectrophotometer and man's hands extending from a lab coat
A spectrophotometer

The popular Sierra Nevada brewery uses this method today, calling it the Spectrophotometric method. A tool called a spectrophotometer is used to read how much light is absorbed in the beer sample while the ultraviolet light shines through it. However, it’s common that other breweries use different ways to measure IBU.

Kudos to you for reading all that scientific mumbo jumbo, but I assume you’re drinking a cold and bitter tall one while reading this anyway, so you should be fine.

What are the Bitterness Measurements of Different Kinds of Beers?

Speaking of Sierra Nevada, the Sierra Nevada Pale Ale has an IBU of 38. This number is common for the American pale ale variety. In comparison, New Belgium’s Voodoo Ranger has an IBU of 40.

The Voodoo Ranger IPA version has a score of 50, which is no surprise as IPAs are famously more bitter than other kinds of beer. Then the number jumps up to 70 for the Voodoo Ranger Imperial IPA.

While these numbers vary, the IBU scale is pretty consistent among certain kinds of beer.

  • American lagers are typically the lowest of 5 to 10 IBUs
  • Hefeweizens have 8 to 12
  • Amber lagers 20 to 25
  • Pale ales 35 to 40
  • American IPAs 55 to 70
  • American barley wine and double IPAs from 65 to 100 IBUs.

To The Bitter End

Man taking selfie of himself and passed out friend with beers in hands

IBUs are not so much a marketing ploy than quality control to craft a consistent brew. But IBUs ultimately should not be used as a quality market by the consumer. Since so much relies on balancing out hoppiness and its other ingredients, a low IBU could mean a beer too bitter for your tastes depending on how it’s made.

Given how unpredictable relying on IBU can be, I hope you find it freeing to just keep trying different kinds of beers until you find your favorite, like Goldilocks finding that perfect bed in that children’s home invasion story.

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