Beer IBUs: How the International Bitterness Units Scale Works

In beer brewing, an IBU rating refers to the International Bitterness Units scale, which measures the relative bitterness of the beer. Brewers shape beer's flavor by balancing notes of sweetness from sugars in the malted grains and the bitterness from hops. The IBU scale standardizes the number of compounds in beer that produce a bitter taste on the tongue and helps brewers manage quality control.

Hops, a fragrant herb, contain alpha acids. When the sugars in the wort convert to alcohol during the brewing process, these bittering compounds undergo isomerization and oxidation, producing iso-acids called isohumulones. The isomerized alpha acids give beer its bitter flavor notes in combination with polyphenols.

The IBU level of beer ranges from 0 to 120. Technically, the bitterness can be higher, but the human palate is less able to detect differences above that range. As the IBUs number increases, the parts per million of iso-alpha acids and polyphenols register as more bitter on the tongue.

In theory, a high IBU beer will taste more bitter than one with a low IBU, but that is not always the case. Beer enthusiasts and homebrewers use the IBU count as one guideline, keeping in mind that flavor is subjective. Some beer drinkers have a high tolerance for bitterness or simply enjoy bitterness more as a flavor.

The balance of sweetness and bitterness can also affect the tasting notes. A smoky stout beer, or an intense, heavy barleywine can incorporate higher IBUs without tasting as bitter as a light-bodied pale ale with the same IBU rating. This is because the beer's bitterness is balanced against the sweetness of the malts.

IBUs are often associated with India pale ales, which are known for their high hop content and bracing bitterness, but more varieties of beer have IBU ratings. Below is a list of the range of IBUs found in various varieties of beer:

1. 1. Sour beer: Sour beers are generally quite low on the IBU scale, usually in the 5–10 range, though some may be as high as 25. There are a few factors for low IBUs: The natural acidity of sour beer works as a good counterbalance against the malt sweetness, the low amount of dissolved sugar, and the fact that some of the microorganisms in the fermentation process are intolerant of hops.
2. 2. Gose beer: Gose beer is a subtype of sour wheat beer style, and like other sours, it tends to be a lower IBU option, from 5–15.
3. 3. Lager: American lagers tend to be lower on the IBU scale, usually in the 5–15 range. Lagers are lighter-bodied and crisp, relying only on enough bitterness to balance the malt flavors.
4. 4. Wheat ales: Wheat ales, mainly Belgian-style wheat ales, are lighter and less robustly sweet than their malted barley counterparts. This beer variety also incorporates fruit or uses yeasts that impart a fruity aroma and flavor profile to the beer, resulting in relatively low IBU numbers in the range of 10–35.
5. 5. Pilsner: Pilsner beer tastes light, crisp, and refreshing. Pilsners tend to have lower-mid-IBU ratings in the 20–40 range, as a slight hoppy bitterness lends bite to their natural crispness.
6. 6. Pale ale: American pale ales are between lagers and IPAs in terms of ABV (alcohol by volume), flavor intensity, body, and mouthfeel. Pale ales are not as malty or heavy-bodied as IPAs, so their usual IBU range of 30–50 can taste more bitter since there is less to counterbalance the bitterness.
7. 7. Stout: As with many beer types, stouts have a range of subtypes. Most stouts, including silky-smooth oatmeal stouts, are on the medium-low side of the IBU scale, around 25–40. Imperial stouts with bolder flavor profiles (and higher ABV levels) will get up into the 50–80 range, challenging and even surpassing some IPAs.
8. 8. IPA: India pale ale tends to have a high perceived bitterness, reflected in its IBU range of 50–70. American IPAs have become remarkably varied as a subcategory of beer, from hoppy, higher ABV Double IPAs or Imperial IPAs with high IBUs to lighter session IPAs. New England-style IPAs are usually lower on the IBU scale; these beers have bright, fruity, and floral notes and aromas from their varied hop additions and types.
9. 9. Barley wine: American barley wine beers tend to be intensely and complexly flavored, with abundant malty sweetness balanced against a heavy, hoppy bitterness. Barleywines can be as high as 100 on the IBU scale, but most are somewhere in the 50–100 range.

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