calculated IBU disparity

[Brewer #174341]

Why do I get drastically different IBU values depending if I enter metric or imperial units?
Entered in oz, I get a final IBU of 43. Entered in g, I get 27.

I suspect it has to do with the lack of precision. In the recipe editor, the smallest imperial unit increment is 0.1oz. The smallest metric unit increment is 0.1g, which is equal to 0.003oz. That's a difference of two orders of magnitude.

It seems to me that if you're using imperial units, don't expect predictable results. I know I can taste the difference between IBU 43 and 27.

 

[I_playdrums]

Trying to put a number value on perceived bitterness seems a bit subjective. Go with what you want to make. Experienced brewers become instinctive about bittering hop additions and know where to draw the line. The software, I think, is a way to help confirm, or not, if the recipe is headed in the right direction. The finished beer will tell the truth. Side note: Is Heady Topper really 100 IBU? Ten years ago that number would be saying " drink me if you have the cajones".

 

[thunderwagn]

I've found that bouncing around on almost any calculator and even from calc to calc can drive one mad. It brings me piece of mind to pick a setting and stick with it and adjust accordingly.
I'm also fairly convinced that no calculator out there is very close in the actual ibu's.

 

[Ozarks Mountain Brewery]

ibu's are relative to the water chemistry and the taster so their is no exact right or wrong constant, it's just one of those things you adjust to your preference, with my water I don't like anything bellow 30 ibu so that or above is what I set my recipes too

 

[Head First]

Why do I get drastically different IBU values depending if I enter metric or imperial units?
Entered in oz, I get a final IBU of 43. Entered in g, I get 27.

I suspect it has to do with the lack of precision. In the recipe editor, the smallest imperial unit increment is 0.1oz. The smallest metric unit increment is 0.1g, which is equal to 0.003oz. That's a difference of two orders of magnitude.

It seems to me that if you're using imperial units, don't expect predictable results. I know I can taste the difference between IBU 43 and 27.

Would effect IBU with changes in how ingredients are entered also. Definately different decimal points. Sometimes when switching back and forth things don't change correctly.

 

[Brewer #174341]

Okay. But why not just another decimal place? Beginners don't have instinct or experience. Oh well guess I'll just stick to metric.

 

[I_playdrums]

I reread the original post, and it sounds like metric is the way to go, with this recipe builder, for the most precise calculation. Don't forget about the age of the hops, boil intensity, and wort pH all having an effect on Alpha Acids and their efficiencies.