What does IBU mean in beer?

Bitterness is good. Maybe not emotionally, but when it comes to flavour, culinary experts agree that a bit of bitterness is better. And that goes double for our favourite bitter beverage – beer.

While most beers are proudly bitter, there’s a huge amount of variation between styles, with a spectrum ranging from delicate bitterness to palate-exploding astringency. Fortunately, you don’t need to be a beer expert to figure that out before tasting a beer, with many breweries including a handy little guide on the back of the package. It’s called IBU and, once you know what you’re looking for, it can be a simple shortcut to finding your favourite flavours.

Scales are great – when you have a frame of reference. Imagine if someone told you the weather in Kelvin – “Leave the jacket at home, it’s a gorgeous 300 degrees out there today”. It’s a number, sure, but it doesn’t really mean much to most of us.

The same goes with IBU, which stands for international bitterness unit. IBU is the standard measurement of bitterness in beer and it can give you a pretty good gauge of how bitter a beer is, if you know what the numbers correspond to. 

Without getting too heavy on the science (check out this research paper if you really want to look under the hood), bitterness in beer mainly comes from a compound called isohumulone, which comes from hops. IBU measures the parts per million of isohumulone in beer, so if you see a beer with an IBU of 20, that’s 20 parts of the bittering compound per million parts of the beer. The human tongue, it turns out, is pretty good at perceiving bitterness.

The IBU scale starts at zero, which is the absence of bitterness, and tops out at around 120 or so, which is considered to be about the threshold of our perceptions (and, obviously, really quite bitter). But we’re still a bit theoretical here, so let’s look at what this means for your lagers and ales.

Here’s a quick tasting exercise: pick yourself a nice Mexican pale lager and take a sip. Pretty smooth, right? Now try a West Coast IPA. Forget, if you can, all the flavour differences, and just think about bitterness. That IPA should be significantly more bitter than the lager, and there's a good reason for that: hops.

Along with water, malt and yeast, hops are one of the four basic building blocks of beer (legally, if it doesn’t have hops, it’s not beer). Historically, hops have been a preservative (the acids in hops help prevent bacteria from growing) and a bittering agent, but they’re also responsible for all those fruity, herbal flavours in beer. 

Hops, as we mentioned above, contribute isohumulone to beer – that chemical compound responsible for bitterness. As a general rule, then, the more hops used, the stronger the bitterness. Mexican lagers don’t use much in the way of hops and, as you’d probably agree, are pretty mild compared to hopped-up IPAs when it comes to bitterness.

Oh, and a little aside: besides the hop content, the overall bitterness of a beer can depend on a couple of other factors. One, interestingly, is genetics (it turns out that some of us just find things less bitter than others) and another is the overall flavour of the beer. For instance, sweeter beers balance bitterness and can be perceived as being less bitter than they really are. Like adding a spoonful of sugar to your coffee, y’know?

Here’s what we know: beer isn’t beer unless it contains hops, and hops contribute bitterness. Some kinds of hops, though, are more bitter than others, and there are even ways to add hops without the bitterness (a technique called ‘dry-hopping’ – but we’ll cover that another day). These are the sorts of complexities and caveats that make the IBU scale so handy because you don’t have to guess – you can just look at the number.

Whether you prefer a bare whisper of bitterness or something that’ll twist your tongue around, consider the below list a good starting point. And remember, the scale runs low to high – low numbers are less bitter, high numbers are more bitter.

• Light/pale lager – 5–20 IBU: Light of body, light of bitterness. The sorts of beers you might pop a wedge of lime in.
• Sour/gose/Berliner weisse – 5–20 IBU: Sour styles don’t tend to lean on bitter hops and can be among the least bitter beer styles, particularly when flavoured with sweet fruits.
• Wheat beer/hefeweizen – 10–15 IBU: Light, dry and easy going, these wheat-based beers are among the least bitter styles around.
• Australian lager/premium lager – 10–25 IBU: Your typical draught lager or premium lager that every Australian state gets parochial about. Often low on other flavours, the bitterness can stick out in some brews but is pretty low overall.
• Stout/porter – 20–50 IBU: Dark beers like stouts and porters can seem rich, sweet and low on hops, but that’s just the malt doing its work – they can actually get pretty bitter.
• Pilsner – 25–45 IBU: A lager that’s hopped up to another level, pilsners tend to be more flavoursome and more bitter than their lighter lager siblings.
• American pale ale – 30–50 IBU: A nice, noticeable bitterness but, generally, plenty of fruity hop flavours and sweet malt keep things balanced.
• Hazy/NEIPA – 30–50 IBU: There’s always an exception to the rule and, while these hazy styles are full of fruity, tropical hops, a few clever brewing techniques mean they tend to be less bitter than West Coast IPAs.
• IPA/West Coast IPA – 50–70 IBU: Hop city, population you. You might hear terms like ‘resin’ or ‘pine’ with some of these to describe the bitter flavours in IPAs.
• Double IPA – 60–100 IBU: It’s an IPA, but more of everything, please. Extra hops mean dialled-up bitterness, but there’s also likely to be a sweet malt keeping it all in check. The biggest name in the bitter game can get even more potent as a triple IPA.