From the HBD Archive
From: (Walter H. Gude)
Subject: IBU <-> HBU revisited...
Date: 1992-03-11 17:12:49 GMT

About a week ago I asked about HBU to IBU conversion. First of all thanks
for the great response. Th summary of which follows:

Josh Grosse (amoung others) writes:

<paraphrase> HBU's may be estimated as

IBU = HBU * (%utilization / (gallons * 1.34)).

Several sources give the %utilization number as 28% for leaf, 30% for pellet,
given a 60 minute boil of "standard" gravity wort (1.040-1.045). Plugging
it all in we get IBU=HBU(or AAU)*~4.5.

While persuing Micheal Jackson's New World Guild to Beer, he references
45 IBUs as extremely bitter. Now my beers with 10AAUs for 60 min. are
not overly bitter. Why? Because like most partial mash brewers, I only
boil about 2.5 gallons of wort. This means my boil has a gravity of about
1.090 for my "standard" beer. And my utilization is obviously far less
than 30%.

Does anyone have a formula for %utilization, incorperating gravity
and boil time?

(I understand that this information may be buried in a Lotus 1-2-3
spreadsheet authored by the infamous Mr. Richman.)

As always, thanks for the help,
Walter Gude

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