Big variation among IBU calculators

[cmmcdonn]

I am preparing for a RIS brewing tonight and I'm getting big differences in IBUs among the different online calculators.

My OG is right around 1.106 set for a 3 gallon boil

Hop schedule:

oz aa time
2.0 13 60 nugget
0.5 4.8 60 willamette
1.0 4.8 30 willamette
0.5 4.8 5 willamette

IBU calculators are giving me results between 59 and 80. All options are correctly entered into the calculators... I've triple-checked that.
edit: 49 - 80. not 59.

I'm not as concerned with knowing the exact IBUs as much as knowing whether or not this is adequate enough for this big of a stout.


Thanks,
Chad

 

[Revvy]

Yup. it all depends on which default scale the software uses. There's plenty of threads on here discussing it. Somewhere it should tell you what the default setting is, and even give you the option to change it. Even on the free Beercalculus website.

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

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/