About Hop Bitterness
This is a calculator for predicting hop bitterness when creating a beer recipe. Hop bitterness in beer is expressed in International Bitterness Units (IBUs). Hop bitterness is the result of the Alpha Acids in hops being isomerized by boiling. The longer the boil (to an extent) and the greater the percent of Alpha Acids in the hops, the greater the Isomerized Alpha Acids that are released into the wort and make their way to the finished beer. Isomerization simply means that it’s the same atoms as the original Alpha Acid in the hops, just arranged in a different way due to the boiling.
Apart from bitterness, hops also impart flavors and aromas in beer. This is done through various volatile oils making its way into the finished beer. In contrast to the bittering aspect of hops, boiling reduces their presence. Please keep this in mind when designing a beer recipe.
The Alpha Acid Percent (%AA) can be found on the hop packaging. This calculator is for whole dried hops moving freely in the kettle. Otherwise, please mind the following:
- If you are using whole dried hops in a muslin or hop spider, then subtract approximately 10% from the IBUs
- If you are using hop pellets, then add approximately 10% to the IBUs
- Hops added at Flame-Out, by Whirlpooling, or through Dry Hopping will not add any IBUs according to the Tinseth equation.