IBU/GU questions

Ok, so I've been reading about the meaning of IBU/GU, to a point that I thought I knew what it meant. Then I went to play a little with brewtarget, and now I'm not so sure.

What I read about it is that IBU/GU means International Bitterness Units/Gravity Units, so I thought it was as simple as a relation between bitterness and ABV. But when I went to BT, I have no way to make sense of it.

For example, I've been playing with a hefeweizen recipe. The OG is stated as 1.054, FG, 1.014, ABV, 5.3%, and IBU, 14.9. The IBU/GU is 0.28.

So, I have 2 questions about it:

1. How do you calculate that? No matter what numbers I use, I can't get that result.

2. How does that number relate to taste, or does it? Does that number help in any way to predict your outcome?

Thanks in advance.

Calculating it is deceptively simple:

Take the numbers after the decimal in OG (e.g., 54 above), divide the IBU (14.9) by that value. 14.9/54=~.28.

As for its predictive value, I've never really used it. I prefer to use the numbers individually to see what I expect. However, it can be helpful when balancing an IIPA to ensure that you don't have nothing but hops with no backbone to support it. I'd imagine an IBU/OG value of 10 or so would be an absolute disaster.

To calculate out IBU/GU, you have to take the last digits of the original gravity. For instance, in your case with an OG of 1.054, you've got 54 GU. Then you can take your IBUs over GUs, or 14.9/54 which is about 0.28. Its really just a measurement of the IBUs vs the strength of the beer.

For instance, if you were going to up your hefeweisen recipe to a double hefeweisen (not sure if it exists, but sounds kinda tasty ), you'd maybe want to keep the ratio about the same. If you were shooting for an OG of 1.072 (72 GUs), you'd want to up the IBUs to about 20.

Personally, I don't use it a whole lot, because some of the difference is also going to come from the FG that doesn't get factored into the equation. Two pale ales, both OG 1.05, 25 IBUs, if one finishes really dry at 1.005 and one finishes at 1.015, the lower FG is going to taste more bitter. But I think it is handy comparing different styles of beer, and gives you a range to shoot for with a particular style when designing a recipe.

Edit: Beat to it!

This should help you understand the relationship.


http://www.brewsupplies.com/hops-gravity.htm

It really help me when I started. I do a copybof that chart with every brew I do and mark where the recipe falls. Really helps understand what you like.

It's a relative measurement- the amount of IBUs to the OG.

It's a good way to sort of figure the bittering units for the style you're making.

For example, many of my IIPAs are over 1.000- and so are some of my IPAs! My "Furiously Hoppy IPA" has an IBU/SG ratio of 1.738! That beer leans so far toward hops, it's unbalanced.

But for my Fat Tire clone, the IBU/SG ratio is .568. That's pretty balanced- an OG of 1.053, and IBUs of 35. My Dead guy- a malt bomb for sure- has an OG/SG ratio of .231!

As you can see, it's not the exact number that really matters. Looking at the ratio is just another helpful tool to make the beer you want to make by comparing the OG to the IBUs.

Thanks everyone.

So, if I understand this correctly, wouldn't it be more accurate (to asses the final bitterness of the beer), to use the final gravity, instead of the original gravity?
I mean, the final gravity is supposed to be in direct relation to the amount of non fermentables left over in the beer, right?

Inodoro_Pereyra said:

Thanks everyone.

So, if I understand this correctly, wouldn't it be more accurate (to asses the final bitterness of the beer), to use the final gravity, instead of the original gravity?
I mean, the final gravity is supposed to be in direct relation to the amount of non fermentables left over in the beer, right?

Click to expand...

Like a lot of things in this hobby, I don't know exactly why it works, but I've found that my beers have improved since I started paying close attention to my BU:GU ratio. I find that it gives me a better indication of how balanced that beer will be than just going by the number of IBU's alone.

It's just another number that you can use to give you an idea about what your beer is going to taste like, and a way to balance the malt and the hops.

Another thing to keep in mind is that 'IBU' is at best an estimate, depending on which calculation is used, I've seen dramatic differences in what is predicted. The point is, for both IBU and IBU/GU is that it gives you a number with which you can establish a baseline.

As long as you always use the same method to calculate, both of these numbers can allow you predict how a beer (especially stylistically similar beers) will taste, and how untested recipes will compare to previous beers.

It's just another tool, and it doesn't really mean anything in a vacuum, but allows you to learn and compare as you go.

Thus, in your example...the .280 would be a very malt forward beer ( as a hef should be) .500 represents a fully balanced beer. I try to make my pale ales at a ratio around .800 and my IPA's closer to 1.150. I imagine a big nasty hop slobberer would be approaching 1.500.

I understand all those numbers are inaccurate to a degree.
My point is, OG is a measure of all sugar/starch content in the wort. FG is the measure of only the unfermentable content, which is the only part of the wort that's gonna balance the hops' bitterness...right?
So if we take the FG, against the SG of a "dry-as-a-bone" brew (0.990), and with that number we calculate against the IBU, we should have a more accurate result.

Am I missing something?

I think this is something that works well within a range, a fairly broad range, but on outliers it will probably be different. I like to think of it and use it as a comparison tool. I don't know how useful it is to compare a high grav IIPA with my blonde/cream ale.

That being said, I do think it's a better number than just IBU alone. I notice that I tend to like beers that have a certain balance, in other words, a certain IBU/GU, regardless of just the raw IBU number.

For example, if I brew a pale, and get an IBU/GU of .8, and think, hmm, that was good, but it could use more bitterness, and I wish it had a little more gravity, I can adjust the grain bill to give more malt, but increase the hops to shoot for a higher IBU/GU and have a pretty reasonable expectation of what I'm going to get...in relation to what I already have.

While you could just go, yeah, raise the grav and the hops, I think this number gives you a more accurate view of where the beer is going.

(full disclaimer) I actually really like this ratio as something that allows me to judge where things are going. It's not perfect, but it lets you judge the balance of the beer by 'the numbers'.

And now to actually think about your question, I don't use much yeast that's going to take anything down to .99, but no matter what the original gravity, you're still going to have 'maltiness' and residual sweetness just from the extracted starches (in fairly predictable, consistent levels/ratios, depending on your mashing profile) and the makeup of grain and nature of the extraction process.

I mean, if I mash the same 2 row at 152, I'm going to get the same sugar/starch profile(s) whether my final gravity is 1.050 or 1.1, right? So then furthermore if I use yeast A in both beers, I'm going to get roughly the same attenuation assuming these gravities are within the parameters of the yeast capability, right? So maybe my point is IBU/GU somewhat assumes that OG is reasonable as an analogue to FG?

Maybe it's a thing that's not as valuable across different yeast or dramatically different attenuation ranges?

Thanks Skiingimpy, I get it now. If you use it to compare different variations of the same beer, for the same attenuation , your numbers would stay accurate just using OG.
I was thinking more about the possibility of establishing a comparison between different styles of beer, so somebody with no beer drinking experience (like myself) would have a better idea of which styles would suit their tastes. So far, I have found a lot of contradicting information about it...

While I think it is GREAT for comparing similar or same styles of beer, I do think it has usefulness outside of that. I do notice, from drinking commercial beers, that I am very fond of beers that happen to be around the .8-1 IBU/GU number. Like pales ales that run in the 1.050 OG (5%abv) and 40-50 IBU number, but also IIPA or barleywines that run 1.1 OG and 80-100 IBUs. I think it's a balance thing that describes the way you perceive sweetness and bitterness.

I hope that makes sense.

That being said, in the end, it is just another parameter that can help improve your brewing and enjoyment of beer.

beergolf said:

This should help you understand the relationship.


http://www.brewsupplies.com/hops-gravity.htm

It really help me when I started. I do a copybof that chart with every brew I do and mark where the recipe falls. Really helps understand what you like.

Click to expand...

Thanks for link, there is a lot of useful stuff there.

I am 1st time brewer and I am preparing for my 1st batch,

I am not sure if I understand this ratio correctly: let say we are brewing Lord Crouchback's Special Bitter (recipe from JP "How to Brew"), OG- 1.045, IBU- 38.
When I put these numbers in graph, it shows that beer will be Extra hoppy.

My question is, is this ratio normal for bitter and should we try to accomplish Evently balanced ratio for all beer we make, or that depends on beer style?

diS-
I've seen that graph around a lot, and I think it is interesting, but I don't know that their definitions of what is balanced, hoppy, malty, etc. necessarily corresponds to what people might perceive and desire.

The point of brewing is to make something that you (and I guess your friends, and the more you get into it, an ever increasing circle of people) like to drink. As I've said before, to me 'balanced' (what I like to drink) falls more in the IBU/GU=.8-1 range. Looking at the chart, that puts most of the beers that I make, and like to drink, squarely in the 'extra hoppy' range, but I don't think my tastes are that far to the 'hoppy' side.

I think there are two factors at work here. 1) I think society (the 'good' beer drinking part) is sliding towards 'hoppier' beers, so the chart is outdated. and 2) different people like different beers.

So the point is: what kinds of beers do you like to drink? to me, anything with 'pale ale' in the style name, (or esb) is going to be 'hoppier' according to that chart. Is that the kind of beer that you like? As long as you've picked a style of beer that you typically like to drink, don't worry about what the chart says. When you're done you'll have beer, it'll be amazing (cuz you made it), and you can make adjustments to the IBU/GU balance, based on what you like, from there.

That is true, different people have different definitions..
I am looking at some recepies and most of them are at extra hoppy side, some of them even falls under that category of chart.

At the end, I have to brew my own beer to know what is my definition of "hoppy".

The chart help but is not the be all end all. I have been putting all of my brews on the chart and as long as I am consistent with how I calculate everything I can get a good feeling for what I like in certain beers. If I make a new recipe and it falls in the same range on the chart I can be pretty confident the I will like the brew.

It is all one big learning experience.

I simply use this chart to figure out the IBU numbers I'm shooting for, then I go back into beersmith to get there.



I've found this helpful even do the second beer in a partigyle on the fly, with my refractometer and and a boil volume calculator. I take a reading of my second runnings, then calculate what the OG will be when the wort is boiled down to 5 gallons, then I look at that chart and decide where I want my hop level to fall, then I calculate a hopping regimen to get there.

Thanks everybody for he replies.

One thing that puzzles me, though: in both that chart and brewtarget, you go from "balanced" to "slightly malty" to "extra malty".
Now, I have read in several threads not to confuse maltiness with sweetness, because they're not the same.
Are they using "malty" to mean "sweet", or there's another parameter to give an idea of the beer's sweetness?

Inodoro_Pereyra said:

Thanks everybody for he replies.

One thing that puzzles me, though: in both that chart and brewtarget, you go from "balanced" to "slightly malty" to "extra malty".
Now, I have read in several threads not to confuse maltiness with sweetness, because they're not the same.
Are they using "malty" to mean "sweet", or there's another parameter to give an idea of the beer's sweetness?

Click to expand...

"malty" and "sweet" are NOT synomous! "Malty" means that the malt flavor is predominant. "Sweet" means that you taste an actual sugary sweet.

I wonder if a different example would be helpful. Maybe something like a condiment like olives. If something tastes like olives, it might have a hint of saltiness, but it wouldn't be just "salty". It tastes like olives. I guess malty is similar. Sure, it's got an undertone of sweet malt flavor, but really malt isn't that sweet. It tastes like malt. A "malty" beer isn't a sweet beer- it's got rich malt flavor. For example, Rogue's Dead Guy Ale is malty. It's a malt bomb. But it's not what I would call sweet.

Yooper said:

"malty" and "sweet" are NOT synomous! "Malty" means that the malt flavor is predominant. "Sweet" means that you taste an actual sugary sweet.

I wonder if a different example would be helpful. Maybe something like a condiment like olives. If something tastes like olives, it might have a hint of saltiness, but it wouldn't be just "salty". It tastes like olives. I guess malty is similar. Sure, it's got an undertone of sweet malt flavor, but really malt isn't that sweet. It tastes like malt. A "malty" beer isn't a sweet beer- it's got rich malt flavor. For example, Rogue's Dead Guy Ale is malty. It's a malt bomb. But it's not what I would call sweet.

Click to expand...

That's what I thought.
So what would be an indicative of sweetness?
I really dislike bitterness. As far as I'm concerned, the most bitter beverage I like is Coca Cola...
So what are the beer styles in the sweet end of the spectrum?

Inodoro_Pereyra said:

That's what I thought.
So what would be an indicative of sweetness?
I really dislike bitterness. As far as I'm concerned, the most bitter beverage I like is Coca Cola...
So what are the beer styles in the sweet end of the spectrum?

Click to expand...

Well, "sweet" can be in everything from blonde ales to stouts! It's funny, because I'm the opposite of you. I do not have a sweet tooth and can not eat anything sweet. I can't even eat Jello as it's WAY too sweet for me!

But, bitter is also not the opposite of sweet! There are many not bitter but not sweet beers.

So what are you looking for in a beer? Not bitter? Or sweet? They are not the same thing.

What are some commercial beers you like?

Let me put it this way: I don't drink coffee, I drink tea. For a cup of tea, I use 3 tablespoons of sugar. Yeah, I said "tablespoons". So you could say I do have a sweet tooth...

I drank beer once in my life, when I was about 5 years old. I couldn't stand it. All I can say about it is it was a "Bieckert Imperial". Probably the most horribly bitter thing I have ever tasted, with the exception of the polio vaccine.

So, basically, I'm looking for what most here would probably qualify as an "undrinkable sweet swill". For my first brew, I'm planning to do a hefeweizen, with 5 Lbs of mango pulp added after fermentation. I figure that'll bring up the sweetness a little...
But I don't want to stay only with a hefe, I want to try different styles. Just I can't find any information about them, other than hefes and witbier...

Inodoro_Pereyra said:

Let me put it this way: I don't drink coffee, I drink tea. For a cup of tea, I use 3 tablespoons of sugar. Yeah, I said "tablespoons". So you could say I do have a sweet tooth...

I drank beer once in my life, when I was about 5 years old. I couldn't stand it. All I can say about it is it was a "Bieckert Imperial". Probably the most horribly bitter thing I have ever tasted, with the exception of the polio vaccine.

So, basically, I'm looking for what most here would probably qualify as an "undrinkable sweet swill". For my first brew, I'm planning to do a hefeweizen, with 5 Lbs of mango pulp added after fermentation. I figure that'll bring up the sweetness a little...
But I don't want to stay only with a hefe, I want to try different styles. Just I can't find any information about them, other than hefes and witbier...

Click to expand...

Your homework has to be to go drink some beer! If you don't know what you like, it'll be hard to make a beer you enjoy. Some people like milk stouts, with the roasty/lactose sweet chocolate flavor, some people like blonde ales, some people like wits, some people like ambers, etc. But without know what you may like, it'll be very hard to find a recipe.

Yeah, I was afraid you'd say something like that...

Thank you Yooper, you've been a great help. Guess I'm gonna have to start drinkin'

Inodoro_Pereyra said:

So, basically, I'm looking for what most here would probably qualify as an "undrinkable sweet swill".

Click to expand...

I wonder if this would fit your bill,

https://www.homebrewtalk.com/f78/vanilla-caramel-cream-ale-23680/

I've never done it but some of the comments, including at least one by yoop from WAAAYYYY back leads me to believe that "undrinkable sweet swill" would be a good name for it.

Thank you Revvy, will definitely try it in the future.