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 Home Brew Forums > Still don't get Beer Calculus IBU formula!
01-25-2012, 12:42 AM   #1
Lodovico
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 Still don't get Beer Calculus IBU formula!

Ok, I've read about 30 posts discussing this topic and I guess I still don't get it. When I compare identical recipes in Beersmith and Beer Calculus, the numbers are still way off.

Both are set for 11 gallon batches and Rager formula for bitterness.

I set my average boil at 12.5 gallons for 60 minutes in Beer Calculus and the IBU numbers are WAY higher in beer calculus. I still don't understand. I mean higher by like 40 IBUs.
What am I still missing? I know it still has to do with boil average because when I leave it at 4 gallon boil average, the numbers get close to what I'm getting in Beersmith.

So when I go to beer calculus and enter:

11 gallon batch size and a 4 gallon boil average for 60 minutes- now the numbers line up closely with my recipe in beersmith. This makes zero sense to me. Can anyone explain this?

For the love of god, don't post links to previous threads on the topic. I just spent 15 minutes reading them all, and it still doesn't make sense to me. I need a better explanation how 11 gallon batches, both using rager formula, same AA, pellet hops, and same addition times can be wildly different (between the two programs) when I enter my actual boil average (12.5 gallons), but are the same when I enter a way different (and incorrect) boil average (4 gallons).

Thanks for the patience.

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