International Bittering Units (IBUs)

Bitterness is a flavor characteristic of beer from the addition of hops during the boiling process. The longer the boil, the more bitter the beer. Using a using a spectrophotometer, bitterness is measured in International Bittering Units (IBUs), with most beers in the 20 to 100 range. Lagers and stouts are generally low in IBUs, while IPAs can be significantly more bitter. Malty, sweet brews can mask bitterness so perceived IBUs may be lower in, for example, a Scottish Ale.