International Bitterness Units scale
character of beer
is measured by the International Bitterness Units scale
, or IBU scale
for short. An IBU is one part per million of isohumulone. The higher number, the greater the bitterness
A light American lager might be as low as 5 on the IBU scale. At the other extreme, a barley wine can range up to 100. Other examples:
One formula craft brewers use to calculate IBU is
hop weight × AA% × utilization × volume × 1.34
- hop weight refers to the weight of the hops used in ounces.
- AA% refers to the alpha acid percentage, which is influenced by many factors, including method of cultivation, species, and time of year. Hops are often sold labeled with this percentage.
- utilization is the percentage of Alpha acid that is actually used during the boiling process.
- volume means the volume of the wort in gallons.
- the constant (1.34) adjusts the measurement to account for the use of U.S. customary units.