IBU discrepancy

Post #1 made 4 years ago
I am just waiting to try my first bottle of a Guinness clone I made recently and I have a question regarding my IBU's.
I was aiming for 46 IBU Tinseth which according to BIABacus I hit the mark but I plugged in the recipe to iBrewmaster on my iPhone and it's telling me the IBU's are 65 Tinseth. Why is this? It was a single addition of hops right at 90 min should I have waited till 60 min?

Tinseth IBU Checker

Post #3 made 4 years ago
Many programs have errors in their IBU calculations. For example they use the gravity into boil instead of the gravity at the end of the boil and/or use the volume into fermentor instead of the volume into fermentor plus the kettle to fermentor loss. One major program had both these errors for many years. Until just now, I was under the impression that they had corrected both errors after we pointed it out quite some time ago but a quick check now shows that both errors are still present unfortunately.

If iBrewmaster has these two errors then it is quite possible for the discrepancy to be as much as you have noticed. I will attach the file we originally wrote to double-check the BIABacus Tinseth measurements against Glen Tinseth's original hop utilsation data.

Because one or both of these errors (and some others) are so widely spread, you should really pay very little attention to any Tinseth measurement that does not match the BIABacus. Focus more on the weight of the actual hop bill and Volume of Ambient Wort of the original recipe if you are lucky enough to be able to determine those.

Feel free to post your BIABacus file here if you want someone to double-check things for you.

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Last edited by Pat on 14 Mar 2014, 10:39, edited 1 time in total.
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