Final Gravity

I could have sworn I saw something to calculate the FG of my brew but for the life of me I can't find where I read it.

Is there a strait forward way of calculating the FG and final alcohol content of your brew?

(og-fg) x 131 = ABV

Perfect, now how do I estimate the expected FG?

You can measure the FG with a hydrometer.

try this http://beercalculus.hopville.com/recipe

Or, if you want to estimate it, you can use Beersmith, or Promash, or a free online one like: http://beercalculus.hopville.com/recipe

EDIT: Damn Doug, you beat me to it!

Brewmate http://www.brewmate.net/ is my favorite free one.

again perfect exactly what I was looking for thanks all

BigB said:

Or, if you want to estimate it, you can use Beersmith, or Promash, or a free online one like: http://beercalculus.hopville.com/recipe

Click to expand...

Promash doesn't estimate the FG. It assumes the FG is 1.012, and allows you to plug in the real value when you know what it is.
Beersmith does estimate the FG, but for the way that I brew, the estimates are at least 5 points higher than I regularly achieve.
You cannot rely on FG's predicted by software unless you have verified that the software predictions consistently match your own results.

-a.

ajf, with that in mind, do you think this sort of software can still be useful for designing recipes? At least a starting point for a first attempt?

ajf said:

Promash doesn't estimate the FG. It assumes the FG is 1.012, and allows you to plug in the real value when you know what it is.
Beersmith does estimate the FG, but for the way that I brew, the estimates are at least 5 points higher than I regularly achieve.
You cannot rely on FG's predicted by software unless you have verified that the software predictions consistently match your own results.

-a.

Click to expand...

Fair enough... I don't use Promash, I should have said "Beertools" (which I don't use either, but does predict FG), but I do use Beersmith, and it is dead on 95% of the time (the other 5% of the time I just assume I had one too many home brews or my efficiency is crazy high or crazy low). I would be curious to know why your beers are drying out so much... 5 points is significant enough to warrant an investigation. Perhaps your efficiency is low or you are overpitching? You can adjust for efficiency with Beersmith (not sure about the others).

EDIT: One other thought... have you checked your hydrometer's accuracy?

BigB said:

Fair enough... I don't use Promash, I should have said "Beertools" (which I don't use either, but does predict FG), but I do use Beersmith, and it is dead on 95% of the time (the other 5% of the time I just assume I had one too many home brews or my efficiency is crazy high or crazy low). I would be curious to know why your beers are drying out so much... 5 points is significant enough to warrant an investigation. Perhaps your efficiency is low or you are overpitching? You can adjust for efficiency with Beersmith (not sure about the others).

EDIT: One other thought... have you checked your hydrometer's accuracy?

Click to expand...

To predict FG, the software has to know what the OG is, and what the actual attenuation achieved by the yeast is.
The OG prediction is a no brainer assuming you have your efficiency worked out, but the attenuation depends on how you mash.
The attenuation figures published by White Labs and Yeast are based on their standard mashes (which may be very different to the way you mash).

I don't think many people would disagree that if you mash at 158F, then you will end up with a higher FG than if you mash at 150F.

I also don't think that most people who understand mashing would disagree that mashing at 150F for 90 minutes instead of 45 minutes will also result in a lower FG

I usually mash for 90 minutes at 150F, and achieve the FG's that I achieve.

Create a recipe in Beersmith that has 10 lb US Pale malt and uses a single infusion full body with no mash out sparge. (158F for 45 minutes) It predicts a FG of 1.015
Then change the mash schedule to a light body with no mash out. (150F for 75 minutes) and It still predicts a FG of 1.015
Frankly, this is B.S, but I'm not sure if B.S is an acronym for BeerSmith or the more commonly accepted definition.

If your mash procedure is similar to those used by the yeast manufacturer and your brewing software, then the FG predictions should be fairly accurate.

If they are different (like in my case), then the FG predictions could be very different.

According to MrMalty, I underpitch. My brewhouse efficiency is 80% (which I don't consider low), and I have calibrated my refractometer which matches my (also calibrated) hydrometer.

-a.

The key is "estimate." If you are consistently getting 5 points difference, you need to adjust your "brewhouse efficiency" or adjust the % average attenuation for your yeast. But in general, If you expect software to be able to have a crystal ball to nail your FG or for that matter OG to an exact point, then you are expecting too much out of an "estimate." My point was this: Beersmith and most other software programs can provide you with an estimate, and it can do so within a couple points, often within 1 point. This is sufficiently accurate for probably 95% of homebrewers. But if you want your free, to at most $20 software, to tell you exactly what your OG and FG is going to be for every situation and every possible variable, then maybe you are not looking for an "estimate," maybe you are looking for NASA level precision.

D0ug said:

ajf, with that in mind, do you think this sort of software can still be useful for designing recipes? At least a starting point for a first attempt?

Click to expand...

I looked at beer calculus and brew mate. I found Beer calculus was much easier to use as a being a beginner. It has its limitations though.

I found this tool to help figure out the weights of other ingredients for my braggot and mead.

http://www.gourmetsleuth.com/cookin....aspx?t=t&foodg=0&foods=brown sugar&fno=19334

BigB said:

The key is "estimate." If you are consistently getting 5 points difference, you need to adjust your "brewhouse efficiency" or adjust the % average attenuation for your yeast. But in general, If you expect software to be able to have a crystal ball to nail your FG or for that matter OG to an exact point, then you are expecting too much out of an "estimate." My point was this: Beersmith and most other software programs can provide you with an estimate, and it can do so within a couple points, often within 1 point. This is sufficiently accurate for probably 95% of homebrewers. But if you want your free, to at most $20 software, to tell you exactly what your OG and FG is going to be for every situation and every possible variable, then maybe you are not looking for an "estimate," maybe you are looking for NASA level precision.

Click to expand...

With all due respect, I don't need to do anything to compensate for deficiencies in BeerSmith, except to be aware that these deficiencies exist.
I use Promash which doesn't pretend to predict the FG.
I am aware that mash temperature, mash duration, % of specialty grains, adequate pitching rates, yeast viability, and adequate oxygenation all affect attenuation but I am not aware of any brewing software that takes these into account (thank heavens). Those programs that report an FG only use the average attenuation values published by the yeast manufacturers, and those figures are based on their standards (which may be very different than those applying to a batch of homebrew).

-a

Funny, I thought the OP's question was about getting an FG estimate. Somehow this discussion has turned into a "bash Beersmith" thread. Shame on me for suggesting to a new brewer a means to get an FG estimate. Further shame on me for suggesting a means to adjust an inexpensive program to better compensate to meet one's particular brewing experience.

BigB said:

Funny, I thought the OP's question was about getting an FG estimate. Somehow this discussion has turned into a "bash Beersmith" thread. Shame on me for suggesting to a new brewer a means to get an FG estimate. Further shame on me for suggesting a means to adjust an inexpensive program to better compensate to meet one's particular brewing experience.

Click to expand...

I suggest that you re-read the thread.
The question was answered in posts 2 and 4
Posts 5 - 7 then gave suggestions for using brewing software for determining the FG
In post 9, I mentioned that brewing software predictions can often be very different to reality.
In post 11, it was you that suggested that suggest that I (not the OP) got such high attenuation, and you would be curious to know why.
I answered that question in post 12.
Then in post 13, you start to tell me (not the OP) that I need to adjust my procedures to match a profile that I already know is wrong for reasons that I explained in post 15.
I'm not bashing BeerSmith. I'm just pointing out that the FG predictions can be very inaccurate, and cannot be relied upon if you want accurate results.

-a.

ajf said:

Promash doesn't estimate the FG. It assumes the FG is 1.012, and allows you to plug in the real value when you know what it is.
Beersmith does estimate the FG, but for the way that I brew, the estimates are at least 5 points higher than I regularly achieve.
You cannot rely on FG's predicted by software unless you have verified that the software predictions consistently match your own results.

-a.

Click to expand...

+1

If your recipe doesn't include any big amounts of unfermentables, like carapils, lactose or crystal malts, most tools will work fine. If it does incluse these ingredients, then the tool is way off when predicting FG as it assumes everything is fermentable.