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Recommended
IBU's for
Beer Styles


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Calculating International Bitterness
Units


The International Bitterness Unit is a measure of the bitterness derived from  hops added during the boil.  This measurment approximates the isomerized alpha-acid content (i.e. the components of hops that provide the perception of bitterness) in the final beer.  A higher value=more bitterness, and a lower value=less bitterness.  Recommended IBU's for beer styles can be found by clicking the link on the left.  This equation is useful in order to determine the hop weight and hop boil time necessary to achieve the appropriate bitterness for the style of beer that you are brewing.   You can calculate it as follows (this equation is derived from a model by Byron Burch in The Homebrewer's Essential Guidebook and uses % utilization figures as specified by Mark Garetz in Using Hops: The Complete Guide to Hops for the Craft Brewer):

 

                               Hop weight (ozs.) x % Utilization x % Alpha Acids
Approximate IBU's  = --------------------------------------------------------------------------------------------------
                                                                7.25

                  Hop weight = weight of hops added for specific duration of boil
              % Utilization = see chart below
                  % Alpha Acids = alpha acid content of hops as specified on label
                  Volume = gallons of wort to be fermented (e.g.  5 gallons)


                 

Boil Time % Utilization
< 6 min 0 %
6 - 10 min 0%
11 - 15 min 2 %
16 - 20 min 5 %
21 - 25 min 8 %
26 - 30 min 11 %
31 - 35 min 14 %
36 - 40 min 16 %
41 - 45 min 18 %
46 - 50 min 19 %
51 - 60 min 20 %
61 - 70 min 21 %
71 - 80 min 22 %
81 - 90 min 23 %