# IBU confusion????

Discussion in 'Beginners Brewing Forum' started by bigdaddy0442, Feb 11, 2021.

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#1
I have calculated the IBU value for a 1 gal batch of Sweet London Stout using multiple calculators on the internet and keep getting a value of between 70 and 92. I took a 5 gal recipe and divided it by 5 for my amounts. I thought a sweet stout should be between 20 and 40. What am I doing wrong? Will the Lactose addition bring the IBU down that much?

Here are my numbers for a 1 gallon batch:

2.5 initial boil volume
Initial boil Gravity: 1.048

Brewers Gold AA% 9%, Weight .4oz, time 60 min.
Fuggles AA% 4.5%, Weight .2oz, time 30 min.

1.6 oz. Lactose

Thanks from a frustrated newbie!

2. ### Josh Hughes Well-Known Member

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#2
Did you use the calculator on here? May have to adjust it once you scale. But you can match the ibu using the software. How long is your boil? 2.5 gallons will take a while to get to one gallon or at least for me I would have. Put the recipe in the brewers friend calculator and adjust from there.

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#3
Last edited: Feb 11, 2021
The reason I tried some of the other calculators was that I got an IBU of 106 using the BF calculator.

I must be doing something wrong. I am in Dallas so the altitude is approx. 300 ft

To get under 50 IBU I would have to reduce by hop time to 15 minutes. Is that ok?

4. ### Josh Hughes Well-Known Member

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#4
When I scale a 5 gallon recipe using the scale function I get different ibu. I jut adjust to fit what it should be at each addition. Lower the amounts to keep ibu where it should for each addition. If you change times you are changing aroma and flavor since the times are for that.

5. ### BOB357 Well-Known Member

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#5
There are 3 commonly used utilization models used in calculators. Tinseth, Rager and Garetz. None of them agree, nor are they accurate when compared to actual IBUs. Select one, Tinseth is the most common, and stick with it, adjusting the bitterness level to match your perception. I use Sierra Nevada Pale as a baseline and adjust my similar Pale Ale recipe to give me the same perceived bitterness level, and then adjust utilization in the brewing software to match the number of IBUs.

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6. ### dmtaylor Active Member

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#6
Well, here's my short-hand calculation method. For 60-minute addition, magic factor of 3.6 * 5 / Volume (1) times the ounces (0.4) and alpha (9) gives... 64.8 from the 60-minute. Yes I just did that in my head.

And for the 30-minute addition, the magic factor changes from 3.6 to 2.6... times 5/1 * 0.2 * 4.5 equals... 2.6 * 4.5 is the same as 1.3 * 9 equals... 11.7 from the second addition.

Then add an extra 1.6. So you have 64.8 + 11.7 + 1.6 = ...

This is an approximation of Tinseth but if you were to measure the IBUs in a lab, I'll bet you would actually get between 65 and 80 IBUs, seriously.

Basically did all that in my head, although the typing here helped a bit. Did not use a calculator at all.

The method to the madness, if anyone is interested:

https://live.staticflickr.com/7891/45991029004_df99d89bc1_o.png

Try it, you might like it.

Sorry your sweet stout recipe is so bitter. Yes, it will be very bitter. And yes, you can reduce the amounts or boil the hops for just a few minutes instead of 30-60 minutes to reduce the IBUs to more reasonable levels.

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#7
Thanks all! I'll just eat more peanuts to cut the bitterness LOL!

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8. ### Mark Farrall Well-Known Member

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#8
Probably more important to look at the bitterness units to gravity units measurement in the details section of the recipe calculator here. IBU numbers don't mean much without knowing your grain bill.

Lactose won't change the IBUs but will change your perception of the bitterness in a lot of cases.

And as Bob's already said, the numbers the IBU calculators give you don't mean that much on their own. It's only once you've played around with different hopping methods and beer styles that you get much guidance from them. To do that pick one formula with one calculator and work with it's limited abilities.

Sorry to say if it's one of your first batches you're largely going blind on the bitterness front.

And the other annoying factor is that IBUs are a really poor way to judge bitterness in a bunch of beer styles. And sweet stouts is one of them.

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9. ### Craigerrr Well-Known Member

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#9

10. ### Frankenbrewer Well-Known Member

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#10
Since I started brewing, I have kinda logged the IBU levels I like in various beers. I use the recipe builder to get me around those levels based on the type of beer and the hops used. I don't know how accurate my hopping is but so far I have only brewed one hop bomb. It was my 4th or 5th batch. It was also before I found this site.