Ibu Question Again

[Willie3]

I was able to come up with three very different outcomes from 3 very different formulas to calculate IBU

I used J. Palmer's site along with another looking for the correct answer. Can someone explain to me why I am coming up with three very different answers.

J Palmers equation

AAU x Utilization (from chart) x Recipe Vol

eg. 6.75 x .147 (< taken from chart) x 75 / 5 = ~15

AAU's in this case is .5 (oz) x 13.5 (% AA)

Other Sites Equations

1 IBU = HBU*4.55

HBU = AAU = 6.75

IBU = 6.75 x 4.55 = ~31

2 IAAU / .01335 / Recipe Vol

IAAU = Isomerized AAUs which @ 60min = 30%

So 6.75*.30 = 2.025

IBU = 2.025 / .01335 / 5 = ~30

SO which one is correct? The last two seem to be close but they are far removed from Mr. Palmer's equation outcome.

I know that IBU Calculations are not absolute but I have to admit if these calculations are more than half off from one another which one do I use to compare to other people's brew? At this point which do I trust is correct and which do I not use?

- WW

 

[Willie3]

Can someone please help me? Maybe I am all frigged up in the head and can't figure this out. So annoyingly confusing.

Thanks

- WW

 

[Ivan Lendl]

I was able to come up with three very different outcomes from 3 very different formulas to calculate IBU

I used J. Palmer's site along with another looking for the correct answer. Can someone explain to me why I am coming up with three very different answers.

J Palmers equation

AAU x Utilization (from chart) x Recipe Vol

eg. 6.75 x .147 (< taken from chart) x 75 / 5 = ~15

AAU's in this case is .5 (oz) x 13.5 (% AA)

Other Sites Equations

1 IBU = HBU*4.55



HBU = AAU = 6.75

IBU = 6.75 x 4.55 = ~31

2 IAAU / .01335 / Recipe Vol

IAAU = Isomerized AAUs which @ 60min = 30%

So 6.75*.30 = 2.025

IBU = 2.025 / .01335 / 5 = ~30

SO which one is correct? The last two seem to be close but they are far removed from Mr. Palmer's equation outcome.

I know that IBU Calculations are not absolute but I have to admit if these calculations are more than half off from one another which one do I use to compare to other people's brew? At this point which do I trust is correct and which do I not use?

- WW

the first one gives you a percent utilization at 15 percent, the other 2 gives you 30 which is more 'right' for a full volume boil

just change the .147 to .3 and that will give you 30 ibu's

i rate mine at 35 percent for 5 gallons and use yet another equation:

weight (oz.) x aau x utilization / 6.7 (or 5 g x 1.34)

so .5 oz x 13.5 x 35/6.7=35ibu's

the only variable is the percent utilization. I rate 60 min @ 35, 30 min @ 17.5, 15 min at 10, and 10 min or less i dont even count

 

[Sephro]

http://www.rooftopbrew.net/ibu.php may be try that?

I just use promash because it's waay easier

 

[Willie3]

You know this post may sound stupid - but I was inclinded to stick with 30. After I found that bittering hops are used 30% of the time I thought that is what I should use. I thank you for your vote of confidence. I will stick with the latter two formulas. As for the chart of utilization - any idea of why its off so much?
.147 came from the chart. .30 came from average utilization of bittering hops.

Thanks

- WW

 

[Walker]

the first one gives you a percent utilization at 15 percent, the other 2 gives you 30 which is more 'right' for a full volume boil

just change the .147 to .3 and that will give you 30 ibu's

Correct. I don't know the source of the other two equations or what the magic numbers in there mean (the 4.55 and the .01335), but maybe those calculations are assuming a full-volume boil, which will have a lower gravity and higher utilization of AA than a smaller volume/higher gravity boil.

-walker

 

[Walker]

You know this post may sound stupid - but I was inclinded to stick with 30. After I found that bittering hops are used 30% of the time I thought that is what I should use. I thank you for your vote of confidence. I will stick with the latter two formulas. As for the chart of utilization - any idea of why its off so much?
.147 came from the chart. .30 came from average utilization of bittering hops.

Thanks

- WW

I honestly think the chart is giving you the right answer if you are doing a partial (less than 5 gallon) boil.

-walker

 

[Willie3]

Thank you Sephro and Bjorn!! The Site you sent me Sephro confirm's Bjorn's response and my hunch!!

Cool. My brew "Stars & Stripes" APA has 30 IBU's - This is exactly what I was going for!!

This is my first batch that I planned out and brewed exactly to my plans - and it worked. Confidence is such a great thing!! No on to AG Batches!!!!

 

[Ivan Lendl]

You know this post may sound stupid - but I was inclinded to stick with 30. After I found that bittering hops are used 30% of the time I thought that is what I should use. I thank you for your vote of confidence. I will stick with the latter two formulas. As for the chart of utilization - any idea of why its off so much?
.147 came from the chart. .30 came from average utilization of bittering hops.

Thanks

- WW

i think 40 percent is the maximum yeild of ibu's, thats what is acheiavable in a lab or pro brewery where they have agitaters to help seperate the hop oils and all that. Us dirt-bag brewers probably cant get 40 percent.
so with a full boil (5-7 g) just assume your getting 30-35 percent @ 60 min(i use 35 because my burner kicks ass, and when i drink my beer that i figured to have 50 ibu's its pretty damn bitter)

 

[Walker]

Thank you Sephro and Bjorn!! The Site you sent me Sephro confirm's Bjorn's response and my hunch!!

Note that that site also assumes you are doing a full volume boil.

If you boiled all 5 gallons, you are set. If you boiled less than 5 gallons, the calculations are going to be off.

What exactly was your recipe, and did you boil all 5 gallons of wort, or did you boil 3 gallons and dilute with water after the boil?

-walker

 

[Willie3]

Yes you are right. So I put in the amount I boiled with and figured out the OG of the wort prior to adding water to bring to 5 gal. I still come up with 30, so I think I pretty safe.

Anything else you can think of would be great too.

Thanks Walker!

- WW

 

[Walker]

Yes you are right. So I put in the amount I boiled with and figured out the OG of the wort prior to adding water to bring to 5 gal. I still come up with 30, so I think I pretty safe.

Anything else you can think of would be great too.

Thanks Walker!

- WW

Just for sanity checking... what is the gravity of your boil?

I know you have 0.5oz of 13.5 AAU% hops and you are making a 5 gallon batch. Are those pellets or whole hops?

I'm playing with the calculators that are on that site, and I can't get 30 IBUs out of it.

Note: BATCH volume should be 5, even if you are only boiling 3 galons.
Wort gravity needs to be adjusted to account for the partial boil.

 

[Willie3]

Wort gravity is 1.077
Pellet Columbus .5oz @13.5%AA
60 min.

 

[Willie3]

There are two calculators - if you use the same information in both you get the same results I got from two different formulas.

Now I am back to square one - one says 15 and the other 30

 

[Ivan Lendl]

Wort gravity is 1.077
Pellet Columbus .5oz @13.5%AA
60 min.

well thats a different story, thats a big beer. Papazain rates a 1.070 wort gravity at 27 percent utilization which will give you, oddly enough, 27 ibu's.

 

[Walker]

OK. I'm getting about 27 IBUs out of the rager calculation.

Based on your original post, I had looked at palmer's chart that you referenced and had concluded that you had a boil gravity of 1.1 (since that is where you got the 0.147 from).

If your boil gravity was 1.10, rager gives 24 IBUs.
If your boil gravity was 1.08, rager gives 27 IBUs.

Sounds like you are close enough to what you wanted. Brew on! :rockin:

-walker

 

[Willie3]

This is the gravity of the boil not the wort in the carboy just prior to pitch.

add to make 5 gals and the gravity is 1050.

- WW

 

[Walker]

There are two calculators - if you use the same information in both you get the same results I got from two different formulas.

Now I am back to square one - one says 15 and the other 30

I don't know how you are using that website, but I get 18 and 27 out of the two calculations.

Regardless, don't use the tinseth method unless you are doing full-volume boils. Use tge rager method. It's more accurate for partial volume boils.

 

[Willie3]

OK so when I calculated the amount of DME to get the Boil Gravity I came up with 1.100 but forgot to add the LME kicker and the .5 lbs Rauch. When I did those conversions I came up with about 7.5 # of DME which brought my Boil Gravity to 1.077. I made sure this was correct several times.

Thanks for your help.

- WW

 

[Ivan Lendl]

This is the gravity of the boil not the wort in the carboy just prior to pitch.

add to make 5 gals and the gravity is 1050.

- WW

the gravity of the boil is the only thing that matters. You should be around about 27 ibu's. Just for reference ive got an 1.050 apa that i used .5 oz columbus 13.3 aau for 60 min, then .5 oz for 30, and its quite bitter!

when i do extract/partial mash beers i just rate my 60 min hops at 20 percent and call it a day.

 

[Willie3]

I only used .5 of Columbus at 60 nothing esle except at flame out.

I used .5 of Cascade and .5 of Columbus for aroma.

 

[Willie3]

No you are correct 18 and 27 are what I come up with. Now that we have that under our belts we can move on. Geese took long enough!! I think the gravity of my blood is 1.077 - making me think this hard only gets me more confused.

Thanks again.

- WW