Glossary
IBU
International Bitterness Units: a laboratory measure of dissolved iso-alpha-acids, in milligrams per litre.
Also called international bitterness unit, international bitterness units, bitterness unit.
IBU is a chemical measurement, and it is a good one — it tells a brewer how much bittering compound made it into the finished beer. What it is not is a bitterness rating.
Perceived bitterness depends on residual sweetness, body, alcohol, carbonation, water sulphate and roast as much as on iso-alpha-acid concentration. A 60 IBU imperial stout tastes far less bitter than a 60 IBU West Coast IPA, because in the stout there is a great deal of sweetness and body to balance against. The number is also silent about hop *aroma*, which is what most modern hop-forward beer is actually built on — a heavily dry-hopped hazy IPA can measure lower than a classic bitter while smelling enormously more hoppy.
BeerHQ therefore stores IBU as a measurement and perceived bitterness as a separate sensory dimension, and never derives one from the other.
Commonly misunderstood
"IBU tells you how bitter a beer tastes." It estimates one compound class. Two beers at the same IBU can differ by a wide margin in perceived bitterness.
Related
- Alpha acid — The hop compound IBU measures the isomerised form of.
- Isomerisation — The reaction during the boil that makes alpha acids bitter.
- EBU — The European convention, measured slightly differently.
More vocabulary
ABV · ABW · Alcohol unit · Alkalinity · Alpha acid · Apparent attenuation · Attenuation · Beta acid · Cohumulone · Degrees Lovibond
See every term on the glossary index.
Last reviewed 2026-08-16.
Evidence
What BeerHQ knows about this, and how. Every statement carries the state of the evidence behind it rather than being presented flatly as fact.
Perceived bitterness depends on residual sweetness, body, alcohol, carbonation, water sulphate and roast as well as on iso-alpha-acid concentration, so two beers at the same IBU can differ substantially in how bitter they taste.
Backed by a source
Sources: Beer: Tap into the Art and Science of Brewing — print; Tasting Beer (2nd edition) — print
International Bitterness Units quantify dissolved iso-alpha-acids in milligrams per litre by a defined spectrophotometric method, and are a measurement of one compound class rather than a rating of perceived bitterness.
Backed by a source
Sources: ASBC Methods of Analysis; Analytica-EBC