Good IBU forumla plus SRM

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Active Member
Mar 22, 2005
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Can someone provide a good IBU formula ?

Also does anybody have a good way to judge the SRM of your finished brew ?

Maybe a comparison to some standard main stream brews or something ?


Well-Known Member
Dec 29, 2004
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San Francisco Bay Area
I would recommend a couple of things. First, get Designing Great Beers. It gets deep into all the technical stuff and formulae as well as the issues involved. If you want to buy it, please use the link to Amazon at the top of this page so the site gets some revenue from the purchase.

Second, download ProMash or Suds or some brewing software and let it calculate your IBUs for you. Much easier than doing it by hand, and it'll take in all the factors.

SRM is actually pretty tricky to assess outside of a lab. They make color comparison cards, and Designing Great Beers talks about comparing to commercial beers. The above software packages will give you a pretty good idea where a recipe will end up. But especially for dark beers, SRM is a tricky beast to really quantify without lab testing.

Fortunately, the software estimations are more than accurate enough for homebrewers. Both ProMash and Suds have trial versions.

FWIW, the formula for IBUs from DGB is:

(Woz x U% x A% x 7.489) / (Vgal x Cgravity)
Woz - weight of hops in ounces
A% - alpha acid percent as decimal (eg 7% = .07)
U% - percent utilization
Vgal - volume of final wort in gallons
Cgravity - gravity correction for grav over 1.050 (1 +[(Gboil - 1.050) / 0.2]

See what I mean? Download some software and you just enter ounces, alpha, and time of boil and it spits out IBU. Software is essential to designing your own recipes IMHO.

Cheers! :D


Well-Known Member
Feb 8, 2005
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Pocatello, Idaho
There is also an online recipe spreadsheet calculator thing that I have used quite abit:

You just plug in the quantities for your recipe, and it will tell you things like what your gravity should be, how many ibu's to expect, how dark it'll be etc. Basically everything a downloaded program will do, but you don't need it to be set up on your computer - all you need is an internet conection.

Oh, and I second Janx in his recomendation of Designing Great Beers by Daniels. It is a very informative book, essential if you want to get into calculating and predicting and other sciencey aspects of brewing. Plus it discusses in depth a variety of beer styles, histories, traditional brewing methods, and describes how award winning homebrewers brewed their versions of those styles.