IBU Calculation Differences

Why do I see such a big difference between different programs like Promash, Beersmith and Brewpal on IBU calculations? Even when they are set to the same standard like Tinseth or Rader I can see a 10-15 IBU difference when calculating recipe IBU's.

Is that difference showing for the same OG?

Tiber_Brew said:

Is that difference showing for the same OG?

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No, the OG is pretty close, just the IBU calculation is giving me fits. I know these are just estimates but I thought they would be closer between different programs. I did an APA recipe today and Promash was 20 IBU's higher than the same recipe in Brewpal and all the other recipies I've put in have Promash higher as well.

Try adjusting the malt bill so that the OG is the same across the board, then reading the IBU estimates from there. If they are still drastically different, there could be other factors coming into play with varying parameters of the software. The true test is to run the same recipe through the different software and comparing the predicted data of those to your specific measured results (OG, FG, SRM, efficiency, etc.). As long as you measured and entered your volumes and constants as accurately as possible, the software that comes the closest might be the one to work with from there on out.

Brewing software tends to be more accurate with better quality inputs. Even then you may have to determine which program suits your process better than the others.

I think I figured it out. I do FWH and there's a huge difference between IBU's that way but when I punch in boil times they are very similar. I guess FWH is still a little unknown and debatable?

From what i've gathered, calculating predicted IBU isn't all that accurate anyway. I remember reading about breweries that have calculated a 180 IBU beer which upon lab testing was under 100. I would think that programs would differ based upon the knowledge and personal experience of the software writer. There are so many factors that affect BU. Even mash Ph is almost impossible to predict accurately, I think Ph affects FWH too so a bit of error would get magnified.

So I have 4 different IBU calculations to chose from on Promash, Rager, Tinseth, Garetz and Generic. They all read different anywhere from 5-20 IBU in a 60 min boil. I guess it's kind a like a crap shoot picking one out and sticking with it to figure your own tastes and bitterness? Is there a more recommended one of these four?

As far as FWH goes I have read that most calculate it the same as a 20 minute boil. My Promash is much higher and only reads a little less than a 60 minute boil but i can edit or change it to reflect a 20 minute boil if that is the general consensus?

There is at least one other difference between Promash and BeerSmith (I don't know about the others).
Promash is set up for the AA% to represent whole hops, and if you change to pellet hops, it increases the AA% used in the calculation by 10%
BeerSmith is set up for the AA% to represent pellet hops, and if you change to whole hops, it decreases the AA% used in the calculation by 10%

-a.

If I remember correctly the brewing network had Glen Tinseth on to talk about the hop formulas awhile ago. He basically said that they are all just approximations and should only be used as guidelines. Also, they were talking about how important it was to stick to using the same one every time you brew and adjusting accordingly. If you calculated 70 ibus on the tinseth scale and it's not as bitter as you want or something you know that with your system tinseth might undercalculate bitterness and you can adjust accordingly on your next brews. I highly recommend listening to the podcast, here is the link http://thebrewingnetwork.com/shows/588

I've found that the Daniels formula estimates much higher IBUs for a given amount of alpha acid units than Tinseth. I've been using Tinseth for a while, and found that the estimated IBUs seem quite short. When I run the same numbers through the Daniels formula, they seem a little more accurate (for my process anyway). Sometimes there is a difference of up to 7 or 8 IBUs between the two.