Brew Calculus vs. Palmer's How to Brew

[therealrsr]

I ran a recipe through brew calculus. As an exercise I also did the calculations manually using Palmer's direction as a guide in an excel spreadsheet. They numbers do not work out. Palmer method gives higher OG and IBU. Pretty sure the factors are near identical in both methods. Can someone explain what I am doing wrong or missing? (I did factor efficiency at the end which isn't in Palmer discussion, but still higher)

 

[david_42]

Probably nothing. Different methods yield different results. IBUs can be calculated using 3 or 4 equations. OG is dependent on the underlying assumptions about sugar availability for each grain and mash efficiency.

The trick is to find an approach that works well with your brewing system and sticking to it. Brew the beer and see where the OG hits.

 

[Revvy]

Without looking at your recipe and crunching numbers a couple things come to mind.

The final volume of a lot of Palmer and Jamil's recipes are usually 5.5 or 6 gallons whereas most of the time we write recipes for the standard 5 gallon recipes. That often accounts for differences between what we might input in software. Make sure the final volume is matching.

The other thing is, like David said, there's several different calculations used to figure out IBU. And they give different numbers. Somewhere in either a book or on the software it should tell you what the default setting is, and even give you the option to change it to match.

Here's an explanation of how Beercalculus calculates it from their Hopville Blog for example;

Previously, the default IBU calculation for Beer Calculus was based on an average of a few popular formulas. It did four calculations (Garetz, Rager, Tinseth, and the legacy Hopville calc) and averaged them together. I chose to blend a few conflicting numbers together instead of committing to a single one by default. That neutral position tended to cause some confusion among both types of brewers: those who cared which formula was in use, but didn’t know you could change it, and those who didn’t care at all. Plus, the only indication that a formula selection was being made was a subtle message “avg” near the IBU result – pretty vague about what was happening behind the scenes. Recipes now default to the Tinseth formula. Hopefully this will satisfy those who prefer this formula, and also clarify the default calculation to folks who don’t really care.

One of the most recent thread discussing this is here. https://www.homebrewtalk.com/f84/different-ibus-provided-different-software-218066/

 

[therealrsr]

Thanks again David and as always Revvy,

I know both were Tinseth Utilization factors. I took the potential grain yields for my spreadsheet from Brew Calc/they nearly match the HBT Wiki but adjusted to take that variable out. If I specify a 5 gallon batch in calc does it auto up the boil volume for evaporation? That's one I had not considered and could be the culprit as the divisor of both. Oh well, getting too academic for the beginner board, time to rdw....(wish I wasn't at work so I could finish that line)