Hop Addition Calculator

[akervin]

Im starting to experiment with recipes, making my own and altering kits, and so Ive been using an IBU online calculator but they all seem to say something different, and not just a little different. Some say 90 IBU's and another says 56 and one will say 74.

Some dont take into consideration your boil volume, for me its about 2.5 gal, and some do. The Higher BG you have the less effect the hops have and you would think that would be considered. Also since were on BG if I do a flame out addition of half my extract then how do I figure IBU's for the lower BG for the hops that I want to add into the recipe.

I thought I would compare to a kit I bought a while back but they didnt include an IBU for the kit.

Whats the most reliable online IBU Calculator.

 

[krazydave]

I had that problem when I was using online calcs also.
Then I discovered Beersmith...

 

[akervin]

I had that problem when I was using online calcs also.
Then I discovered Beersmith...

Sorry had to edit this post. I confused beersmith with strangebrew software... ill give it a try

 

[krazydave]

Yeah, I agree... setting it up was a bit tedious and mind-numbing and this is coming from a system admin who's been working on computers for over 10 years. But once you get everything in there, it does calculate for just about everything.
I will say that it took me about 4 trials of it before I finally just said "ok, I'll buy the damn thing already".

It is important to spend the time to set up your equipment profile first. After that it's not too bad.

 

[akervin]

Yeah, I agree... setting it up was a bit tedious and mind-numbing and this is coming from a system admin who's been working on computers for over 10 years. But once you get everything in there, it does calculate for just about everything.
I will say that it took me about 4 trials of it before I finally just said "ok, I'll buy the damn thing already".

It is important to spend the time to set up your equipment profile first. After that it's not too bad.

Ill give it a shot. thanks

 

[helibrewer]

THIS IS FOR 5 GALS

Factors: 60 min boil = 4, 30 min boil = 1.4, 10 or less min = .7

IBU's = %AA x ozs x factor

For other batch sizes divide by the ratio of your batch size to 5 gallons which is .5 in your case so:

IBU's = (%AA x ozs x factor) / .5

 

[akervin]

THIS IS FOR 5 GALS

Factors: 60 min boil = 4, 30 min boil = 1.4, 10 or less min = .7

IBU's = %AA x ozs x factor

For other batch sizes divide by the ratio of your batch size to 5 gallons which is .5 in your case so:

IBU's = (%AA x ozs x factor) / .5

Great formulas. seems like easy math to me.

My batch size is 5 gallons... my boil size is 2.5-2.75 gallons... The higher your boil gravity the more hops you need. does that not necessarily matter?

 

[helibrewer]

The formula just relates to BATCH size...gravity is not considered. Gravity does make a difference but boiling times are more significant. If you keep your boil gravity moderate by adding a large percentage of extract late, the first formula would work fine for you since you are doing 5 gallon batches. I think the concensus is to keep the boiling gravity below 1.050-60 for partial boils.

 

[akervin]

The formula just relates to BATCH size...gravity is not considered. Gravity does make a difference but boiling times are more significant. If you keep your boil gravity moderate by adding a large percentage of extract late, the first formula would work fine for you since you are doing 5 gallon batches. I think the concensus is to keep the boiling gravity below 1.050-60 for partial boils.

So if my OG at 5 gallons is suppose to be 1.06-1.065 then I should add about 50 percent of extract at or around 10 mins. is that what your saying.


Thanks for all the reply's..

 

[helibrewer]

If the pre-boil gravity for the recipe is say 1.050, then IDEALLY you would want your partial boil volume to be at that 1.050 also, whatever amount of extract that is at your partial boil volume (2.5 - 2.75 in your case)....that way the hops have no idea they are in a partial boil....then during the last 10 min add the rest of the extract....doing it this way you don't have to adjust your hops for a partial boil.

 

[helibrewer]

So if my OG at 5 gallons is suppose to be 1.06-1.065 then I should add about 50 percent of extract at or around 10 mins. is that what your saying.


Thanks for all the reply's..

LME is about 1.036 per pound per gallon of water. If the pre-boil gravity for a full boil recipe is 1.045 then if you were to partial boil 2.75 gallons you would need 45 points x 2.75 gallons = 123.75 gravity points. divide that by 36 (LME points per pound per gallon) to get 3.44 pounds of LME....so you would use 3.44 pounds of LME in your 2.75 gallon partial boil to give you the same boiling gravity as a 5 gallon full boil.

Then add the remaining LME at 10 minutes remaining

 

[akervin]

LME is about 1.036 per pound per gallon of water. If the pre-boil gravity for a full boil recipe is 1.045 then if you were to partial boil 2.75 gallons you would need 45 points x 2.75 gallons = 123.75 gravity points. divide that by 36 (LME points per pound per gallon) to get 3.44 pounds of LME....so you would use 3.44 pounds of LME in your 2.75 gallon partial boil to give you the same boiling gravity as a 5 gallon full boil.

Then add the remaining LME at 10 minutes remaining

So my recipe calls for 6.6 lbs LME and 1 lbs DME so by my math that's

44 x 1 = 44
36 x 6.6 = 237.6
Total = 281.6

I wanna add the DME before the boil so I don't worry about charing so I should add 2.2 lbs of LME and 1 lbs DME to reach my ~1.045 boil gravity.

I think I've got it. Thanks really appreciate it.

 

[frozt]

The equation for SG from PPG is something like this:

( (lbs. * ppg) + (lbs. * ppg)... ) / batch size (gallons)
So similar to what you did above:

( (44×1)+ (36×6.6) ) ÷ 5 gal. = 56.32 = 1.056

Not sure if that's what you're after or not, but for reference, the PPG of most ingredients can be found on this page, where PPG is the integer form of potential gravity(e.g. 1.036 = 36 PPG).

For IBU calculations, I'd recommend Tinseth's Equations. These take into account both the gravity of the boil and the time factor. The equations on there may be a little confusing at first, but I actually use a slightly simplified equation:

IBU = AAU * hop utilization * 75 / batch size(gallons)

If you don't want to deal with the utilization formula, there's a table on the page that is also accurate. Note that the above equation is for each hop addition as the utilization is different based on time the hops are boiled and the gravity of the boil at the time that you add them.

Let me know if you'd like some sample calculations and I'd be happy to post some of mine.

Cheers

 

[ncbrewer]

For IBU calculations, I'd recommend Tinseth's Equations. These take into account both the gravity of the boil and the time factor.

I use these formulas in my spreadsheet, but have never been sure about how to account for late extract addition. I use the average gravity, e.g. 45 minutes at 1.022 and 15 minutes at 1.089 for an average of 1.039. Do you think any more refinement is needed?

 

[helibrewer]

I use these formulas in my spreadsheet, but have never been sure about how to account for late extract addition. I use the average gravity, e.g. 45 minutes at 1.022 and 15 minutes at 1.089 for an average of 1.039. Do you think any more refinement is needed?

In the reading I have done, average gravity is an acceptable method. Although some utilization will drop off after the final extract addition, I don't think it's worth the math headache to try to adjust for it. I believe the IBU threshold for taste is +- 5 IBU's so it's not that critical.

Getting correct post boil gravities and volumes is the first concern.

 

[frozt]

If you are concerned with getting your estimated IBUs as close as possible, you can calculate late extract additions by calculating separate boil gravities for each hop addition.

In other words, use the PPG equation to calculate the grav. of what is in the boil at the time you add each hop addition (the utilization formula factors in boil gravity). Using late extract additions could make a fairly substantial difference, since you could be doubling the amount of extract as you add the late addition.

I had to do this sort of thing recently with my current recipe, where I add honey in the last 20 minutes, after another hop addition. Here's how I calculated IBUs on that recipe:

Busty Brunette Blonde
(Ska True Blonde Ale Clone)

OG: 1.052
FG: 1.013
ABV: 5.1%
IBUs: 14.99

2.5 gallon boil, 5 gallon batch

4 lbs Pilsen DME
1 lb. Wheat DME
1 lb Munich 10L
4oz Honey (or 1/3 cup) (last 20 min)

.5 oz US Perle 6.5% (60 min)
.5 oz Tettnang 4.8% (30 min)
1 oz Cascade 6.4% (5 min)
.5 oz Tettnang 4.8% (5 min)

Wyeast 1187 Ringwood Ale Yeast
or Danstar Windsor Ale Yeast
Note: 1187 can be slow to start (up to 90 hours)

4 lbs. Extra Light/Pilsen DME 3 SRM 43 PPG
1 lb. Wheat DME 8 SRM 43 PPG
1 lb Munich 10L 10 SRM 35 PPG
4 oz Honey 1 SRM 35 PPG

MCU = ( (4*3) + (8*1) + (.25*1)+(10×1)) / 5 = 6.05
SRM = 1.4922×(6.05^.6859) = ~5.13 SRM

Calculated OG = ( (4×43)+(43)+(1×35)+(.25×35))÷5 = 51.75 = 1.052

Expected ABV = 5.1%

Boil OG (Pre-Honey) = ( (4×43)+(43)+(1×35))÷2.5 = 100 = 1.100

-----------------------------
.5 oz US Perle 6.5% (60 min)
-----------------------------
Util(60) = (1.65×(.000125^.100))×((1−(e^(−.04×60) ) )÷4.15) = 0.147172093 * 1.1 (pellet hops)= 0.161889302
AAU (Perle 60) = .5 * 6.5 alpha = 3.25 AAUs
IBU (Perle 60) = 3.25 AAUs * 0.161889302 util * 75 / 5.0 gal. batch = 7.892 IBUS

-----------------------------
.5 oz US Tettnang 4.8% (30 min)
-----------------------------
Util(30) = (1.65×(.000125^.100))×((1−(e^(−.04×30) ) )÷4.15) = 0.113105401 * 1.1 = 0.124415941
AAU (Tettnang 30) = .5 * 4.8 = 2.4 AAUs
IBU (Tettnang 30) = 2.4 AAUs * 0.124415941 util * 75 / 5.0 gal. batch = 4.479 IBUs

-------------------------
Boil OG (Post-Honey) = ( (4×43)+(43)+(1×35)+(.25×35))÷2.5 = 103.5 = 1.104

-----------------------------
1 oz Cascade 6.4% (5 min)
.5 oz US Tettnang 4.8% (5 min)
-----------------------------
Util(5) = (1.65×(.000125^.104))×((1−(e^(−.04×5) ) )÷4.15) = 0.028303401 *1.1 = 0.031133741
AAU (Cascade 5) = .5 * 6.4 alpha = 3.2 AAUs
IBU (Cascade 5) = 3.2 AAUs * 0.031133741 util * 75 / 5.0 gal. batch = 1.494 IBUs

AAU (Tettnang 5) = .5 * 4.8 alpha = 2.4 AAUs
IBU (Tettnang 5) = 2.4 AAUs * 0.031133741 util * 75 / 5.0 gal. batch = 1.121 IBUs

Total IBUs = 7.892+4.479+1.494+1.121 = 14.99 IBUs


Sorry for the ridiculous amount of text; I hope it makes some sense. I tried to bold some of the important numbers so they wouldn't be lost in the equations. As you can see, I calculated a different boil gravity for before adding the honey vs. after the honey is added. The relevant boil gravity was used in the util equation for the hop additions that occur afterward. Again, for your calculations, you can just use the table on Tinseth's page for getting the Util figure.

 

[ncbrewer]

Frozt – I had assumed that once the late addition extract is added, the utilization will decrease. Instead of using gravity of 1.100 for the first hop addition, I would use the time weighted average of 1.100 for 40 minutes, and 1.104 for 20 minutes – or 1.101. In your example, it makes almost no difference, but I often add 75% of the extract late. In that case there’s a lot of difference. What do you think?

 

[frozt]

You are correct - higher gravity = lower hop util. In my example, as you said, since I'm adding such a small amount of honey the difference is almost negligible. When you do late extract addition though, the difference in util. is considerably greater.

For example, glancing at tinseth's table, a boil grav. of 1.030 at 60 min is .276 util., whereas a boil grav. of 1.060 at 60 min is .211 util., or a ~30% difference in utilization in this example.

So in short, your assumption is correct - for recipes with bigger differences in the boil gravities, using the average gravity will be less accurate.

 

[frozt]

I decided to make up a contrived example just to see the difference in figures. I made something based roughly on your quoted "25% now, 75% at the end" method. Here's what I found:
(5.0 gallon batch, 2.5 gallon boil)

2.0 lbs Pale Liquid Extract (PPG = 36) (60 min)
6.3 lbs. Pale Liquid Extract (last 20 min)
1 oz Cascade 6.4% (60 min)
1 oz Cascade 6.4% (5 min)

OG = (8.3×36) ÷ 5 gallon batch = 59.76 = 1.060

Boil Grav. (Pre-Late-Addition) = (2.0 × 36) ÷ 2.5 = 28.8 = 1.029

Util(60) = (1.65×(.000125^.029))×((1−(e^(−.04×60) ) )÷4.15) = 0.278576741 * 1.1 (pellets) = 0.306434415
AAU(Cascade 60) = 1 oz * 6.4 alpha = 6.4 AAUs
IBU(Cascade 60) = 6.4 AAU * 0.306434415 util. * 75 / 5 gal. batch = 29.418 IBUs

Boil Grav. (Post-Late-Addition) = (8.3 × 36) ÷ 2.5 = 119.52 = 1.120
Util(5) = (1.65×(.000125^.120))×((1−(e^(−.04×5) ) )÷4.15) = 0.024512589 * 1.1 (pellets) = 0.026963848
AAU(Cascade 5) = 1 oz * 6.4 alpha = 6.4 AAUs
IBU(Cascade 5) = 6.4 AAU * 0.026963848 util. * 75 / 5 gal. batch = 2.589 IBUs

Total IBUs = 29.418+2.589 = 32.007 IBUs
----------------------
Conversely, if you do this using the average of the boil gravities:

Boil grav. = (1.029+1.120)÷2 = 1.0745 = 1.075

Util(60) = (1.65×(.000125^.075))×((1−(e^(−.04×60) ) )÷4.15) = 0.184247971 * 1.1 (pellets) = 0.202672768
AAU(Cascade 60) = 1 oz * 6.4 alpha = 6.4 AAUs
IBU(Cascade 60) = 6.4 AAU * 0.202672768 util. * 75 / 5 gal. batch = 19.457 IBUs

Util(20) = (1.65×(.000125^.075))×((1−(e^(−.04×5) ) )÷4.15) = 0.036730617 * 1.1 (pellets) = 0.040403679
AAU(Cascade 5) = 1 oz * 6.4 alpha = 6.4 AAUs
IBU(Cascade 5) = 6.4 AAU * 0.040403679 util. * 75 / 5 gal. batch = 3.879 IBUs

Total IBUs = 19.457+3.879 = 23.336 IBUs

Here, using the average of the boil gravities results in a difference of almost 10 IBUs.

 

[ncbrewer]

Thanks for the info. I'm also following another thread: https://www.homebrewtalk.com/f39/ipa-late-lme-addition-ibu-307399/ There is some discussion about new theories on hop utilization that seem to be very different. Very interesting reading.