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 =
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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 % |
|