What is 'IBU' and what does it measure?

• A. IBU stands for International Bitterness Units and measures perceived hop bitterness from isohumulone compounds; higher numbers indicate more bitterness.
• B. IBU stands for International Brewing Unit; measures color.
• C. IBU stands for Internal Beer Utility; measures alcohol content.
• D. IBU stands for International Balance Unit; measures aroma strength.

Answer: (B)

IBU measures bitterness in beer, based on hop-derived compounds called iso-α-acids. The term IBU stands for International Bitterness Units, and higher numbers correspond to more perceived bitterness. This metric specifically gauges hop bitterness, not color, alcohol content, or aroma. Color is tracked with SRM or EBC, alcohol content with ABV, and aroma is a sensory attribute influenced by hops, malts, and brewing conditions. Since IBU is a chemical proxy for bitterness, actual perceived bitterness can vary with malt sweetness and serving temperature, but in general a higher IBU signals a stiffer hop bite.