What is “IBU” in Beer?

If you’re interested in brewing, you may have come across the term IBU.

But what is IBU in beer? Is it a good thing or a bad thing? How might it influence which beverage you choose at a bar? And what does it have to do with home brewing?

There’s a lot of confusion and misunderstanding wrapped up in those three little letters. We’re here to put that right! We’re going to explain what IBU means, and what it tells you about your beer. And we’ll check out some other strange terms you might have come across too.

So if you’re ready, let’s find out more!

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What does IBU stand for?

Although you may sometimes see it written as Ibu, IBU is actually an acronym.

It stands for International Bitterness Units.

That sounds like a unit of measurement, and in fact, that’s exactly what it is. It also sounds like it measures how bitter the beer will taste. But that isn’t actually what it does – or not quite, anyway.

Bitterness is, after all, subjective. Think about food, for example. What might taste bitter to a white chocolate lover could be perfect for someone who loves 70 percent cocoa solids! And IBU is intended to be rather more scientific than that.

It actually measures the quantity of specific chemical compounds in the beer. The compounds in question are polyphenols and two types of alpha acids, isomerized and oxidized. It measures a few other kinds of compounds too.

What all these substances have in common is that they tend to give the beer a bitter flavor. In many cases, a beer with a higher IBU will taste more bitter than one with a lower measurement. But that’s not the whole story.

IBU and flavor

The way we experience the flavor of beer doesn’t just depend on the number of bittering compounds it contains. It’s also about the complex interaction between those compounds and other ingredients. These can either intensify or balance out the bitter flavors.

If your beer uses hops with a stronger malty flavor, for example, that will serve to regulate the bitterness. That means amber ales might not taste as bitter as you’d expect, even those with a higher IBU. Compared to a light ale with a lower IBU they may, in fact, taste less bitter.

How can I tell the IBU of my beer?

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Beer can have a very wide range of IBU values, from around 5 all the way up to 120. The higher the figure, the more bittering compounds the beer will contain. Almost all beers fall within the 15 to 80 IBUs range.

Different beer styles also typically have different IBUs. At the lower end of the scale, you’ll find lambic, wheat beers and American lagers. Expect these to have anything from 0 to 26 IBUs.

Barleywine and IPAs tend to be at the opposite end of the scale – between 34 and 120 IBUs. Note the size of that range, though. There are lots of different levels within these categories.

Somewhere in the middle, you’ll generally find pilsners, porters and bitters, with between 18 and 50 IBUs.

If you’re buying a craft beer in a bar, the IBU value may be included on the menu.

What is the point of IBU?

If the IBU is an imperfect measure of the bitterness you’ll taste in your beer, what is the point of it?

Well, it’s a useful tool for brewers, who use it to help ensure consistency between different batches. To do this, they use a process called spectrophotometric.

This involves taking a sample of the beer and adding acid and what’s called a non-polar solvent. These substances encourage the bittering compounds to separate out from the rest of the beer. After they’re added in, the mixture is shaken for about 30 minutes.

A sample is then taken of the part of the mixture that contains the bittering compounds. A device called a spectrophotometer then shines a light through the liquid and records how much light is absorbed. This figure is then multiplied by 50 to give the IBU.

The same measurement between batches means you’re likely to get a similar flavor from each batch. That makes it a great quality assurance tool. What the measurement doesn’t tell you, though, is how much you’ll like the taste.

What about IAA?

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You may have come across another measurement of bittering compounds in beer.

The IAA value stands for isomerized alpha acids, and it’s similar to IBU.

If the beer has been brewed with fresh hops, the IAA value will be pretty much the same as the IBU. But if the hops in the beer have gone stale, the IAA value will be lower. Some types of hop extracts used in brewing can also have this effect.

Last but not least, there’s the European Bitterness Unit, or EBU. While IBU is used in the USA, EBU is used in – you’ve guessed it – Europe.

The measuring process is very similar for both scales, but there are some minor differences. Whilst in most cases, the same beers will have the same IBU and EBU, these differences can theoretically result in different numbers. If that happens, the EBU value will be slightly lower.

Alcohol by Volume

If IBUs won’t give you the whole picture when it comes to measuring beer, what other measurements can you use?

There are a whole range of different scales that can help you get a deeper understanding of your beer. One of the best known is ABV, or alcohol by volume.

This tells you how strong your beer is – in other words, how much alcohol it contains. The ABV is a percentage figure, indicating how many parts of alcohol there are to every 100 parts of beer. The higher the figure, the stronger the beer.

Beer color

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Another three-letter acronym you may have come across is SRM – Standard Reference Method. This is a way of grading the color of beers.

Once upon a time, the color was measured in “degrees Lovibond”. This has largely been replaced by SRM, and its sister scale, EBC – the European Brewery Convention. Both scales use a photometer to measure the way light passes through a liquid.

At the lower end of the scale, you’ll find the paler colored beers, like pale lagers and pilsners. These have an SRM of 2 and an EBC of 4. The scale passes through blonde ales, to bitters, to dark lagers. The highest values go to stouts, with Irish stout having an SRM of 24, and imperial stout at 40.

Beer gravity

Beer gravity is used in the calculation of a beverage’s alcohol by volume. It’s an important tool for homebrewers, who can use it to measure the progress of their brew. And it can also help to tweak recipes to try out new styles and flavors.

Gravity is measured with a tool called a hydrometer. It measures how dense the wort – the sugary substance that makes beer – is compared to the density of water. This measurement is known as specific gravity or SG.

The higher the alcohol content of the beer, the lower the SG will be. By measuring SG before and after fermentation, the brewer is able to see how much sugar has been converted to alcohol.

The measurement before fermentation is known as the original gravity, or OG. The one afterward is the final gravity or FG. A simple formula is then applied to the two measurements to give the beer’s alcohol content.

What about XXX?

You may see some beers marked with three or even four Xs. Traditionally, this seems to have been used to indicate strength. The larger the number of Xs, the stronger the beer.

Some people believe the marking to have a very long history, dating back to its use by medieval monasteries. The Xs were believed to be a mark of quality, as well as signifying how strong the beer was.

An alternative theory is that it started life as part of the tax system back in the seventeenth century. Beer above a certain alcohol limit attracted a tax of ten shillings per barrel. X was marked on barrels on which tax was due – X being the Roman numeral for ten.

Over time, brewers began to add extra Xs to show their beer was even stronger. Think of it like a seventeenth-century marketing device!

Today, those Xs a similar marketing function. They won’t tell you much about the style or flavor of the beer, but they help them stand out on the shelf.

Some brewers have even incorporated the X rating into beer names. The Australian beer Castlemaine XXXX (pronounced “four-x”) is one well-known example.

So in summary …

There are a lot of different scales that can tell you different things about a beer, from its strength to its color. IBU tells you something about its bitterness, but it won’t give you the whole picture. And there’s no such thing as a “good” or “bad” IBU.

It’s most useful for brewers wanting to check that different batches of beer are consistent. But if you want to know how bitter a beer tastes, there’s no better tool than your tongue!

So next time you see an IBU value on a beer, you’ll know what it’s telling you – and what it isn’t. Cheers!

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