IBU Hops Bitterness

IBU Hops Bitterness Calculator

This is a calculator for predicting hops bitterness when creating a beer recipe. Hops bitterness in beer is expressed in International Bitterness Units (IBUs). Hops 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.

Using Hops

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 the presence of these volatile oils. 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 leaf hops moving freely in the kettle. Otherwise, please mind the following:

• If you are using whole dried leaf 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 or by Whirlpooling will not add any IBUs according to the Tinseth equation used in the IBU Hops Bitterness Calculator. In reality though, some IBU’s are added as isomerization of Alpha Acids does not instantly stop below boiling.
• Dry Hopping will not add any IBUs under most any circumstances.

Designing a Hops Schedule

Flavor from hops are apparent relative to other flavors in beer. There is no single best time to add hops to a boil as all hops are different and it depends on what you want, but here are some rough guidelines:

• Bittering Hops – Boil for a long time. Usually around 60 minutes or the beginning of the boil.
• Flavoring Hops – Boil for less time, but not a really short time. 30 minutes or less.
• Aroma Hops – Boil for a really short time, if at all. 10 minutes maximum to the end of the boil. Also can be steeped after the boil while the wort is still warm. Dry Hopping in the Fermenter imparts Aroma as well.

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