IBU (International Bitterness Units)
The IBU measures the degree of bitterness of a beer.
The higher the value, the more bitter the beer.

This unit indicates the amount of alpha acids from the hops — that is, the compounds responsible for the bitter taste.

• 0 to 20 IBU: mild, low-bitterness beers (light blond, lager)

• 20 to 45 IBU: balance between malt and hops (pale ale, amber ale)

• 45 to 70 IBU: pronounced bitterness (IPA, double IPA)

• 70 IBU and above: very bitter (imperial IPA, some stouts)

The perceived bitterness also depends on other factors: the malt content, the gravity and the serving temperature can soften or accentuate it.