Beer Smith IBU Calcs differ from J.Palmer How to Brew

Lately I've changed my IBU calculations to include Gravity Factor (Beer Bigness) and utilization. I got my information from John Palmer's How to Brew web page chapter 5.5 ( http://www.howtobrew.com/section1/chapter5-5.html ) .

In his test case a beer with an OG of 1.080 has a total of 31 IBU's.
1.5 oz of 6.4% AA Perle hops (60 minutes)
1 oz of 4.6% AA Liberty hops (15 minutes)

Now I just installed a copy of Beer Smith and it comes up with 38.1 IBU's for this same recipe.

Is someone wrong, or is IBU calculation more of an art than a science.

cefmel said:

Lately I've changed my IBU calculations to include Gravity Factor (Beer Bigness) and utilization. I got my information from John Palmer's How to Brew web page chapter 5.5 ( http://www.howtobrew.com/section1/chapter5-5.html ) .

In his test case a beer with an OG of 1.080 has a total of 31 IBU's.
1.5 oz of 6.4% AA Perle hops (60 minutes)
1 oz of 4.6% AA Liberty hops (15 minutes)

Now I just installed a copy of Beer Smith and it comes up with 38.1 IBU's for this same recipe.

Is someone wrong, or is IBU calculation more of an art than a science.

Click to expand...

IBU Calc's are not an exact science. There are three major formulas, Reager, Tinseth, and the one i can't remember. They are all different, and you will get different results for each. My suggestion is to brew a batch of brew you are use to. That is, it is a known. Then note the difference in beer smith. What beer smith will do, is make your recipe IBU calc's consistent.

Thanks for the reply. I'll stick with what I've been doing for now and see how it goes.

There are some online recipe calculators that will help you determine IBUs.

I know there are on-line calculators, but I have a customized Excell spreadsheet that calculates everything(OG,IBU's,Brix trasnslation, ABV,ABW etc.) for me and I just want to make sure it is correct. I've gotten very use to using it and it's easier than going out to the internet and re-typing in the same information that's already been entered into the spreadsheet.

The on-line calculators don't seem to indicate which formula they are using so if the web site goes down and you have to switch to another web site, there could be consistency problems.