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IBU math question!

A customer wanted me to measure out "enough Magnum for 200 IBUs". I called him and asked him what he meant and he said that the magnum is the bittering hop for all his 5 gallon batches. He needs 15 IBUs here, 30 IBUs there, ect. When he adds all his IBUs up from across his batches it is around 200. So he needes the amount that will satisfy that. So can anyone think of a way to calculate that amount? I know it will change by pre-boil gravity and such but Im looking for a ballpark equation.


aerobatix's picture

For a quick down-n-dirty calc for a 60 min boil addition, divide the IBUs by 3 and then divide by the AA percentage to get the amount of hops in oz. For example, say you have 10% AA Magnum, and you need 100 IBU. 100/3/10 = 3.3 oz. NOTE: This is based on a 5 gal batch using pellet hops.

There are plenty of online calculators, including ones built into brewing software. These calculations are based on pre&post boil volume, utilization, and of course Alpha Acid content. Utilization  changes with boil/steep time, and also hop type (e.g. pellet vs. whole)

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