• Welcome to the new forum! We upgraded our forum software with a host of new boards, capabilities and features. It is also more secure.
    Jump in and join the conversation! You can learn more about the upgrade and new features here.

why are ibu's so far off

itsratso

Master Brewer
Joined
Jul 9, 2013
Messages
74
Reaction score
0
almost any recipe i copy online and enter into beersmith is off, sometimes ridiculously off on the ibu's. i have searched for an explanation for this online and have not really seen a reasonable explanation, is there one? just now i copied jamil's helles recipe: his ibu's: 18.1 - bs ibu's: 14.5 (well outside of the style's range). most people i have heard say to just brew the beer as written and it will turn out fine. is this the consensus or should i try to adjust the ibu's in beersmith?  :-\
 
One explanation I can think of is the difference in reported %AA on the hops. BeerSmith uses a default value that is typically in-range for the particular hops, and this default value can vary from what your package may say. It is a good practice after procuring your hops to touch-up your recipe by entering the exact %AA as shown on the package. This ensures that, at least, you will be entering into BeerSmith the actual %AA you will be putting into the pot.

Another explanation could be the timing of the hops addition(s). The earlier you add your hops, the more utilization you will get and BeerSmith will show this in their calculations. Move your hops around with respect to time and you will see your IBU value move along with it. When copying a recipe, be sure your timing is adjusted to match their timing for hop additions to give the calculators the best possible chance of arriving at the correct IBU value.

Another possible explanation is the particular recipe's method of reporting its IBUs - there are a few methods of doing this, among them are Tinseth and Rager - each with its own reasoning and slightly different means of making the calculations. Some recipes are published using Rager for reporting the IBUs, some use Tinseth. Each will give you a different value when formulating your recipe. While each method has its merit, most folks tend to just pick one and stick with it. No one method is "technically better" than another, it's just a matter of what works for you. BeerSmith defaults to Tinseth. Try going into BeerSmith and select the Options button located just above the recipe field and hit Bitterness in the left column, now change the Bitterness Formula from Tinseth to Rager and see if your recipe looks more like what you expected.

Any one of these possible explanations could be the key to your recipe's IBU inconsistency - play around with these adjustments to see what works for you.

<edit> I ran the numbers from Jamil's recipe, which was done using another brewing program, and sure enough; it was done in Rager. When I put it into BeerSmith, I got 14.6 IBU (after adjusting the %AA to 13.5 as in Jamil's recipe). I then changed the Bitterness Formula to Rager and got 18.1. Note - you will need to change screens to get this change to take affect in your recipe. You can just click the Starter button above your recipe field and then back to Design and you should see the change in IBUs.
 
thanx for your reply phil. I have looked around online and found similar explanations. I have tried the different methods for calculating the ibu's - rager did help a little but still pretty far away from the recipe's reported ibu's. I also tried changing the hops alpha to match the ones reported by jamil which didn't help. but I did not know about clicking the starter button to reset the numbers, perhaps this will help. however (I am not at home right now so I will play with it tonight and report back) I am sure that I saw the ibu's change when I did the above so I am pretty sure that it was the updated numbers. but you taking the time to put in the numbers and having them come out correct means that there is an answer to this. let me get back to you later on this.
 
Back
Top