# Combining hops and Calculating IBU

### Help Support Homebrew Talk:

#### iparks81

##### Well-Known Member
I've looked high and low I cant come up with the way to calculate Alpha acid content of multiple mixed hops....Argh

For instance If I was to Mix:

1 oz Centennial @ 10%AA
1 oz Cascade @ 7%AA and
.5 oz Chinook @ 12.5

I would now have 2.5 oz hops, but how can I determine the AA% or AAUs to put into software to come up with an accurate IBU count???

thanks guys!

OP

bump

#### m3n00b

##### Well-Known Member
Use a program like beersmith or qbrew(free)

#### runkelia

##### Well-Known Member
I've looked high and low I cant come up with the way to calculate Alpha acid content of multiple mixed hops....Argh

For instance If I was to Mix:

1 oz Centennial @ 10%AA
1 oz Cascade @ 7%AA and
.5 oz Chinook @ 12.5

I would now have 2.5 oz hops, but how can I determine the AA% or AAUs to put into software to come up with an accurate IBU count???

thanks guys!
1 x 10 = 10AAU
1 x 7 = 7 AAU
.5 x 12.5 = 6.25 AAU

Next step: We need to know how long you boil each of these, and what you volume goal is, 5 gallons?
And we need to know your boil gravity

#### Calder

##### Well-Known Member
Most programs can take multiple hop additions at the same time. I assume yours can't.

I also assume you are mixing these up and adding them all at the same time.

What you have is (1×10 + 1×7 + 0.5×12.5)/2.5 = 9.5

When mixed together, you have 2.5 ozs of a 9.5 AA hop blend.

#### runkelia

##### Well-Known Member
^^ Not sure what you did there.
IBUs are calculated per hop addition as they are boiled (Utilized) for different lengths of time.
You don't need software to figure out IBUs, It can be done by each hop addition then take the sum. I can figure it out easy enough if you tell me your volume, gravity and boil times for each hop.
Reference John Palmer "How to brew" 3rd ed. pages 56 - 58.

OP

#### iparks81

##### Well-Known Member
Im using beersmith for this recipe, it is the same hops used in DFH 90 min, but a slightly different schedule and different malt bill

3 oz amarillo gold @ 8.8%AA
1 oz Simcoe @ 12.7%AA
1 oz Warrior @ 16%AA

Here is the Schedule
.25 oz @ 90 min
.25 oz @ 60 min
.5 oz @ 30
.5 oz @ 25
.5 oz @ 20
.5 oz @ 15
.5 oz @ 10
1 oz @ 5
1 oz @ 0

and some dry hops

Ive made this beer 4-5 times, and it turns out great, but Ive never bothered figuring out the IBU's

If its more trouble than its worth I've got no problem walking away from it....dont care..TASTES GREAT

If I go The AAU method Ive got 54 AAU's, but figuring out the IBUs from that and the boil time is my issue.

Thanks for the replies!

#### Calder

##### Well-Known Member
^^ Not sure what you did there.
IBUs are calculated per hop addition as they are boiled (Utilized) for different lengths of time.
You don't need software to figure out IBUs, It can be done by each hop addition then take the sum. I can figure it out easy enough if you tell me your volume, gravity and boil times for each hop.
Reference John Palmer "How to brew" 3rd ed. pages 56 - 58.
Did you read the original post? He wants the alpha acid content of a mix of hops. I'm reading it that he took those hops in those quantities, put all of them in a bowl and mixed them up. In a similar manner that Falconers Flight is a mix of different hops. I then assume he is going to take different amounts of this mix and add it to the wort at different times. To calculate his IBUs, he needs the combined AA content of the mix.

#### runkelia

##### Well-Known Member
You are right, I did not understand that he was mixing them up.
OK, Here goes
Assumptions: 1.050 gravity
5 gallon batch

3 x 8.8 = 26.4 AAU
1 x 12.7=12.7 AAU
1 x 16 = 16 AAU
(26.4 + 12.7 + 16) / 3 = 18.37 AAU avg.

IBU = AAU x U x 75 / 5
U values are from How to Brew pg. 58

IBU90 = (.25)(18.37) x (.247) x 15 = 17 IBU
IBU60 = (.25)(18.37) x (.231) x 15 = 16 IBU
IBU30 = (.5)(18.37) x (.177) x 15 = 24 IBU
IBU25 = (.5)(18.37) x (.16) x 15 = 22 IBU
IBU20 = (.5)(18.37) x (.14) x 15 = 19 IBU
IBU15 = (.5)(18.37) x (.114) x 15 = 16 IBU
IBU10 = (.5)(18.37) x (.084) x 15 = 12 IBU
IBU5 = (1)(18.37) x (.046) x 15 = 13 IBU

TOTAL 139 IBU

#### Calder

##### Well-Known Member
3 x 8.8 = 26.4 AAU
1 x 12.7=12.7 AAU
1 x 16 = 16 AAU
(26.4 + 12.7 + 16) / 3 = 18.37 AAU avg.
I didn't follow everything you did, but have to ask if you made a mistake in the work above. I think you should have divided by 5, and not 3. It is impossible to have an average that is higher than any you are using.

#### runkelia

##### Well-Known Member
You are correct, I shouldn't do math while drinking my brews. I may take another stab at it tomorrow, would like to verify the gravity though.

#### runkelia

##### Well-Known Member
Assumptions: 1.050 gravity
5 gallon batch

3 x 8.8 = 26.4 AAU
1 x 12.7=12.7 AAU
1 x 16 = 16 AAU
(26.4 + 12.7 + 16) / 5 = 11.02 AAU avg.

IBU = AAU x U x 75 / 5
U values are from How to Brew pg. 58

IBU90 = (.25)(11.02) x (.247) x 15 = 10 IBU
IBU60 = (.25)(11.02) x (.231) x 15 = 10 IBU
IBU30 = (.5)(11.02) x (.177) x 15 = 15 IBU
IBU25 = (.5)(11.02) x (.16) x 15 = 13 IBU
IBU20 = (.5)(11.02) x (.14) x 15 = 12 IBU
IBU15 = (.5)(11.02) x (.114) x 15 = 9 IBU
IBU10 = (.5)(11.02) x (.084) x 15 = 7 IBU
IBU5 = (1)(11.02) x (.046) x 15 = 8 IBU

TOTAL 84 IBU

OP

#### iparks81

##### Well-Known Member
That Looks great, Thank you guys for this. just a question..where do you come up with these numbers

thanks again...my OG should hit about 1.078. so I can punch this info into Beersmith and get a good Idea of where Im standing.
Just a question..where do you come up with the numbers in bold

IBU90 = (.25)(11.02) x (.247) x 15 = 10 IBU
IBU60 = (.25)(11.02) x [B](.231)[/B] x 15 = 10 IBU
IBU30 = (.5)(11.02) x (.177) x 15 = 15 IBU
IBU25 = (.5)(11.02) x (.16) x 15 = 13 IBU
IBU20 = (.5)(11.02) x (.14) x 15 = 12 IBU
IBU15 = (.5)(11.02) x (.114) x 15 = 9 IBU
IBU10 = (.5)(11.02) x (.084) x 15 = 7 IBU
IBU5 = (1)(11.02) x (.046) x 15 = 8 IBU

#### runkelia

##### Well-Known Member
The numbers in bold are the Utilization coefficient (U), reference "How To Brew" page 58.
You match up the gravity with the boil time on the chart, and it gives you that number.
So now that I know your gravity is 1.078 and not 1.050, all of the Utilization numbers I had plugged in are wrong.
Therefore those IBU values are wrong.

OP

#### iparks81

##### Well-Known Member
Right on, thanks! well...now that I know where to find those coefficients in How To Brew I can do my final calculations...

thanks again runkelia! and everyone else!