IBUs: Recipator vs. Formula

[Somerville]

I'm having a bit of a trust problem.

My Brewmaster's Bible says the formula for IBUs is:
(Oz x AA x Utilization (boil time Ex. 60min = 30)) divided by 7.25.
My perle hops are 7.7% @ 60 min. This formula comes up with 31 IBUs while Recipator comes up with 12.4.

Who do I trust?
I don't have enough experience to make a judgement though I brewed a pale ale with 1 oz of Perle at 60min and it was more bitter than SNPA though another oz of cascade at 30 and 10...any thoughts?

 

[Shambolic]

Are you only doing partial boils? Your formula is probably based on boiling all of the wort.

 

[Somerville]

Yeah I thought about that. I think recipator factors in wort boil and malt right? Its only a 2.7gal boil.

Ok, new question--Who here trusts recipator with their batches?

 

[homebrewer_99]

I don't "trust" Recipator, but I do use it, not so much to formulate my recipes, but to track my input/notes. I like the layout.

I add my ingredients, but I don't trust the numbers.

 

[El Pistolero]

Ok, new question--Who here trusts recipator with their batches?

Recipator gives you a choice of two different methods for calculating IBUs...Rager and Tinseth. According to this site, Tinseth is more accurate for highly hopped beers, while Rager is better for lightly hopped beers. If you use the proper method (Rager in your case), I think you'll see that Recipator agrees more closely with your calculations.

To answer your question...I didn't trust Recipator for IBU calcs until I read the above, but once I started using the appropriate method I found that Recipator is pretty accurate.

 

[Kaiser]

I use BeerSith and I learned not to trust the IBU number that it gives me. My 25 IBU pale Ales taste to others like 30 IBU beers. I assume that the hop-utilization in my system is better than expexted. But I trust that there is a constant factor and when I try to make the same beer again I aim for the same IBUs that BeerSmith gave me before.

Kai

 

[El Pistolero]

My 25 IBU pale Ales taste to others like 30 IBU beers.

I thought most people couldn't tell the difference between 25 and 30 IBU.

 

[cweston]

I use recipator, and I typically use the Rager method with a custom factor, which I found (by trial and error) "calibrates" the recipator IBU numbers with the recipes in Clone Brews and Beer Captured. (The authors allegedly use Rager.)

It's not an exact science, but as Kai said, the important thing is to know that a 40 IBU beer *from your brewery* is more bitter than a 30 IBU beer from your brewery. Once you settle on a method and stick with it, the IBU number for your system will be meaningful to you and will be a meaningful predictor of what the beer will taste like.

 

[cweston]

Here's an interesting example:

Here (http://hbd.org/cgi-bin/recipator/recipator?group=3&item=5637) is a recipe I designed on recipator and just posted there a couple days ago.

You can see it is 40 IBUs w/ Rager and the custom factor of .83.

If you eliminate the custom factor and switch to Tinseth (you can do this by following the "edit recipe" link), it changes to 48 IBUs. If you stick w/ Rager and just eliminate the custom factor, you get 49 IBUs.

So at least we know what range it's in...

BTW, here's the thing that bugs me about the recipe database there: it's very hard to tell whether the creator of the recipe has actually brewed it yet or not. You'd think people would wait until they've tasted the results before posting a recipe, but I suspect many don't.

 

[Glibbidy]

Here is something I hacked into an excel spreadsheet that my mentor worked out with me. I trust him, therefore I trust this formula, which is done by hand as opposed to some fancy schmancy software.

https://www.homebrewtalk.com/showpost.php?p=74370&postcount=14

You guys remember how to use a pencil and calculator right?
I'll throw in the pun now, since I'm setting my self up.

Accountant's work it out with their pencils.

 

[Somerville]

Volume ( gallons)*Target IBU*(OG-1.050/.2+1)*(target IBU/260 +1)*1.01

Divided by: Percentage Utilization* Percentage Alpha Acid* 0.749


Here is the formula you have.
In terms of Volume, is that how much your boiling?
What do all the "+1"s mean? I ask because the only reason why someone might not just make it 1.2 or 261 would be because they change...
Lets see..
2.7 x 28 x (1.071-1.050/.2+1) x (28/260+1) x 1.01
divided by
30 x 7.7 x 0.749
It comes out to 8oz of Perle needed . Obviously there is something in the formula that needs adjusting, could you help me with this?

Note: This is for a strong altbier I'm making

 

[cweston]

Just use the recipator and RDWHAHB. Do you have a specific reason for not trusting the recipator's IBU calculations?

 

[Somerville]

Just use the recipator and RDWHAHB. Do you have a specific reason for not trusting the recipator's IBU calculations?

The whole time I haven't been paying attention to Tinseth or Rager..I ran a couple of recipes from Brewmaster's Bible and found out I need to be using Rager...theres usually a 10IBU difference! I'm curious to know why but I don't need to know.
Thanks for bearing with my stupidity

No wonder my pale ale is so bitter...

 

[cweston]

Did you account for boil size? That makes a really large difference in hops utilization.

Also, your initial post mentions that you boiled Perle for 60 and added Cascade at 30 and 10.

Did you include those in the recipator calculation? Hops added at 30 minutes will still make a fairly significant contirubution to the IBUs.

If the book you mentioned is your primary reference point for recipes, than I suggest doing what I did: type in 3-4 different recipes from your source, and find the method and "custom factor" that calibrates the recipators IBUs to the books IBUs.

 

[Glibbidy]

Volume ( gallons)*Target IBU*(OG-1.050/.2+1)*(target IBU/260 +1)*1.01

Divided by: Percentage Utilization* Percentage Alpha Acid* 0.749


Here is the formula you have.
In terms of Volume, is that how much your boiling?
What do all the "+1"s mean? I ask because the only reason why someone might not just make it 1.2 or 261 would be because they change...
Lets see..
2.7 x 28 x (1.071-1.050/.2+1) x (28/260+1) x 1.01
divided by
30 x 7.7 x 0.749
It comes out to 8oz of Perle needed . Obviously there is something in the formula that needs adjusting, could you help me with this?

Note: This is for a strong altbier I'm making

Volume= gallons of beer you are making, i.e. 10 gallons, 5 gallons. This is your end result, not the total volume of water you are using in your wort.

As for all the "1"s do your calculation and then add that 1. ie.,

(1.071-1.050/.2+1)= 1.105 OR

1.071-1.050 + 1 =1.105
.2
Let me know if this makes sense. I can PM you the excel sheet if you like.
how many gallons are you making?

 

[Somerville]

cweston: I took all that into account. I did that with my book and found out I need to use the rager method. Thanks for the idea! I don't think I would have ever thought of that.

glibbidy: Ok, that makes more sense. I'll give it a whirl but most likely I'll stick to recipator. My final batch size will be 5 gal--usual.

Thanks!

 

[Glibbidy]

I did the math and came up with 1 oz. based on the following information you provided.

Volume= 5 gallons
target IBU's= 28
OG= 1.071
% Utilization= 30
%AA = 7.7

Out of curiosity what does the fancy software calculation give for an amount?

 

[Somerville]

I did the math and came up with .54 ounces based on the following information you provided.

Volume= 2.7 gallons
target IBU's= 28
OG= 1.071
% Utilization= 30
%AA = 7.7

Yeah, if I were to end up using Perle, thats most likely all I would really want to put in it. I find Perle to be pretty harsh if not balanced.
Would you have to lower the target IBUs for 60min hops if you were going to also do 30min hops? Then add the results

 

[cweston]

It seems like the volume needs to be the boil volume, not the final volume.

I just played with recipator. It says that 1 oz of whole leaf Perle 7.7% AA boiled 60 minutes in 5 gallons of 1.071 wort will yield 31 IBUs by the Rager method (close to your result).

But, if I increase the boil size to 6.5 gals (and therefore the intial SG of the wort is 1.055) the IBUs by Rager are 35. This makes sense because lower SG means higher hops utilization.

FWIW, if you scale the Rager result by .83, which is my calibration factor, you come out with 27 IBUs for the 5 gallon boil--almost exactly matching your result.

 

[Somerville]

Yeah, I agree, it should be boil volume or is boil volume in glibbidy's spreadsheet because he calculated mine based off of 2.7 gals and .5oz Perle and got ~28 IBUs and it is ~half of your recipator calculation which is 5 gal and 1 oz of Perle which means you would get roughly the same IBUs...I think...well, you did.

 

[todd_k]

I thought most people couldn't tell the difference between 25 and 30 IBU.

The average person CAN tell the difference between 5 IBU's, anything less than 5 and they can't tell the difference. Most homebrewers CANNOT tell the difference between a change of only 5 IBU's, it needs to be higher. This is due to most homebrewers drink much more hoppy beers than the average person.

 

[Glibbidy]

Yeah, if I were to end up using Perle, thats most likely all I would really want to put in it. I find Perle to be pretty harsh if not balanced.
Would you have to lower the target IBUs for 60min hops if you were going to also do 30min hops? Then add the results

From a standpoint of efficiency you would lower your target IBU's & the efficiency proportionally to the amount of time left in the boil.

Bascially I recommend you use a lower AA hop & strive for at least half of your IBU's in the kettle addtion. Then break up the rest of the IBU's over the middle and late additions. Since you are going to have to add more hops due to the fact that you wil get less percetnage utilization. IMHO you end up throwing some hops away.

In my brewhouse I count on the following based on a 90 minute boil:
25% 80 minutes left in the boil
15% 30 minutes left in the boil
5% 10 minutes left in the boil

consider thes hops and IBU's for your alt. You might be pleasantly surprised
Hops---------------- IBU's--addtion
Tettnanger -----------30 Kettle
Hallertauer tradition--- 10 Middle
Hallertauer tradition----10 Late

 

[Somerville]

In my brewhouse I count on the following based on a 90 minute boil:
25% 80 minutes left in the boil
15% 30 minutes left in the boil
5% 10 minutes left in the boil

consider thes hops and IBU's for your alt. You might be pleasantly surprised
Hops---------------- IBU's--addtion
Tettnanger -----------30 Kettle
Hallertauer tradition--- 10 Middle
Hallertauer tradition----10 Late

Actually mine is slightly similar. Those kinds of hops were my original intention. I'm basing my hop additions off what I have in store. I'm using
1oz tettnanger at 3.5% for 60min
1oz Saaz @ 3.3% for 60 min
1oz Saaz @ 3.3% for 30 min

I would use hallertauer but I have Saaz and Saaz matches the style guidlines though it is chzech.
Altbiers traditionally have minimal hop flavor and I believe close to or no hop aroma. I'm scratching the aroma hops.
I'm going to be using 7lbs of DME and 3lbs of grain (partial mash).
I got 30 IBUs from Ragor method on Recipator. I think I'm good. Everything is in the style range.

 

[Glibbidy]

I'm sure you'll make a fine beer!
What is the breakdown of those IBU addtions? Are you going 20 and 10?

 

[Somerville]

I'm sure you'll make a fine beer!
What is the breakdown of those IBU addtions? Are you going 20 and 10?

I dont know, I would have to run it through recipator again. Should have saved it, oh well. Off to work

 

[budbo]

But I trust that there is a constant factor and when I try to make the same beer again I aim for the same IBUs that BeerSmith gave me before.

Seems to me that is the bottom line.. When I get around to buying the licsense for promash I will compare my recipator stuff to what promash gives me.. (knowing the tinseth/rager thing is $$ ... But I know what 40IBU/20IBU etc tastes like from my brews based on the recipator.... I think the key here is being consistent....

 

[jcarson83]

Seems to me that it doesn't really matter what method you use to calculate IBU as long as your consistent. There is such a large discrepency when various forumlas are used you could be off as much as 25% or more.

The ultimate goal is to brew beer of a consistent bitterness for the desired recipe. If its not bitter enough the first time add more hops and record your data in order to develop a feel for it.

Edit: The problem is you don't know what method the recipe used most of the time to determine the IBU. Therefore calculation is useless except for your own records.