IBU calculation help

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Pharmguy

Pharmguy

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I am finding several different ideas on IBU calculations. Anybody have a good formula? I used beersmith and 2 different books and all 3 came up with different numbers.

I had 1.00 oz Northern Brewer 7% for 30 min boil and 1.00 oz Northern Brewer 7% for 5 min boil. Beersmith gave me 16 IBU's. The Papazian book came out to 21 and this other book (forgot the author) came out to 24.
 
Its going to depend on the wort as well as the hops/time.

For instance a 60 minute hop addition:
An ounce of NB hops @ 8.25% = 37.7 IBU in 5 gallons of 1.040 wort
An ounce of NB hops @ 8.25% = 35.8 IBU in 5 gallons of 1.060 wort
An ounce of NB hops @ 8.25% = 32.7 IBU in 5 gallons of 1.080 wort
 
This is what I've been using.

Glenn Tinseth's Hop Utilization Page

Summary:

IBU= AAU x mg/l of AA

AAU = Bigness Factor x Boil Time Factor
mg/l of AA = (AA% x oz x 7490)/gallons


Bigness Factor = 1.65 x .000125^(og-1)
Boil Time Factor = (1 - 2.71828^(-.04 x time in min)) / 4.15

Hope I didn't make any mistakes but I'm sure someone will correct me if I did.

Edit: the ^ symbol means to the power of.
Edit: Old notes sorry, fixed it.
 
Pick either Tinseth, Rager, or Garetz, even though you get different numbers, as long as you always use the same formula, you'll know what your getting.

I use rager just because that's what Jamil uses and I brew alot of his recipes. (they are all so damn good!)
 
I've been using Ray Daniels method from Designing Great Beers. He has charts in there for what your Utilization Percentages will be, formulas for Gravity Corrections, and tons of other great info.

Assuming you finish with 5 gallons of wort 1.050 or less, your IBU's would be 25.16

Formula is.....

oz x % Utilization x %AAU x7489
5
 

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