Understanding abv calculators.

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sodbuster

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Refractometers measure light refraction through a sugar solution. Alcohol in solution will skew the reading. The refractometer calculator corrects this reading. Give it OG and apparent FG measured in Brix, it'll spit out true FG in SG.

The ABV calculator assumes OG and FG are true gravities as one would get by using a hydrometer or refractometer with calculator.
 
DBhomebrew said:
Refractometers measure light refraction through a sugar solution. Alcohol in solution will skew the reading. The refractometer calculator corrects this reading. Give it OG and apparent FG measured in Brix, it'll spit out true FG in SG.

The ABV calculator assumes OG and FG are true gravities as one would get by using a hydrometer or refractometer with calculator.
Click to expand...
True that. I checked my newest batch with a refractometer Friday, and got 1.042. Hydrometer, five minutes later, read 1.016.

My new rule: check OG with refractometer, and FG with hydrometer.
 
DBhomebrew said:
Refractometers measure light refraction through a sugar solution. Alcohol in solution will skew the reading. The refractometer calculator corrects this reading. Give it OG and apparent FG measured in Brix, it'll spit out true FG in SG.

The ABV calculator assumes OG and FG are true gravities as one would get by using a hydrometer or refractometer with calculator.
Click to expand...
+1. Indeed. It depends if you are using a hydrometer or a refractometer. The first link is for hydrometer readings only. The third link is for refractometer readings only. The second link... you don't really need.
 
BrewZer said:
True that. I checked my newest batch with a refractometer Friday, and got 1.042. Hydrometer, five minutes later, read 1.016.

My new rule: check OG with refractometer, and FG with hydrometer.
Click to expand...
That is the route I am going to go with. I really like the Idea of a Tilt but the consensus is that it is not accurate for final gravity either.
 
sodbuster said:
That is the route I am going to go with. I really like the Idea of a Tilt but the consensus is that it is not accurate for final gravity either.
Click to expand...


you would think, I have seen side by side comparisons using tilt, hydrometer and refractometer and the tilt was the most reliable. Remember you need to adjust for temperature. And for the self correcting devices, they correct less effectively the further they move along the temp range for which they were designed. Also, you need to calibrate your devices.



lastly, it's all irrelevant anyway. IMO, most readings from home brewers are inaccurate (just take a look at how many post on the subject don't read a hydrometers meniscus correctly ). Unless you are dealing with a stuck fermentation or dialing in some advanced fermentation techniques, and you know exactly what pH and ions were on your water, the numbers aren't really going to make much of a difference. You'll still drink and enjoy your beer, and you'll likely never be able to tell by taste if your beer was a few points off (and perhaps even better than designed.

Fwiw (I have an iSpindel). If you calibrate your Tilt correctly. and it doesn't get stuck on Krause, it's nice to know when fermentation is leveled off without having to let O2 get to your beer. My refractometer lets me take quick reading but I only care about being in the ballpark. And my hydrometer is useful for double checking the other two (when I talk the time to cool wort/beer down to 60°

Keep leaning about gravity reading techniques and devices. It's good to know, and reducing user error will make your day more relaxing.

RDWHHB
 
just to give a more complete picture....6.6 Brix is actually a final gravity of 1.002

1673212465479.png
 
bracconiere said:
just to give a more complete picture....6.6 Brix is actually a final gravity of 1.002
Click to expand...
That seems way too low. What refractometer conversion calculator are you using? I don't buy it. Anyway... it's not appropriate to use a calculator like that unless the 6.6 Brix was measured with a refractometer. If it originated from a hydrometer, then FG 1.026=1.026. Be careful not to perform a double conversion. If the 6.6 Brix was indeed measured via refractometer (which I don't think it was), then it should like like this, per Terrill:

1673213666866.png


http://seanterrill.com/2012/01/06/refractometer-calculator/
Or like this, per Brewer's Friend (Novotny):

1673213789661.png


https://www.brewersfriend.com/refractometer-calculator/
The unfortunate part of all this is that Novotny is more accurate when FG>1.014, and Terrill is more accurate when FG<1.014, such that the best calculator in the universe would take a guess where the FG actually falls and then use whichever calculator that was.

But, we digress, because I believe the OP is using a hydrometer anyway, not a refractometer. OP, please confirm. If true, then ABV calculation is very simple:

ABV = (OG - FG) * 131

Which is consistent with the first link in the OP's original post.
 
sodbuster said:
Take those B numbers and punch them into Refractometer Calculator - Brewer's Friend
Click to expand...
dmtaylor said:
But, we digress, because I believe the OP is using a hydrometer anyway, not a refractometer. OP, please confirm. If true, then ABV calculation is very simple:
Click to expand...


i will digress, but most hydros triple or not, read in SG/Plato/ABV....not brix..... brix is a wine thing, for refracs.....

edit: and:

https://www.homebrewtalk.com/threads/using-a-refractometer-i-am-confused.702391/
 
Last edited:
To continue the digression, no hydrometer reads Plato, Brix, or potential ABV. Hydrometers measure specific gravity (which is equivalent to density in g/ml). Plato and Brix are concentrations (grams of sugar per 100 ml of solution). While there are tables that let you convert from one to the other under certain assumptions -- that's where the Plato scale on your hydrometer comes from -- the actual measurement is something different. The distinction is important, for example, at the end of fermentation when the specific gravity will be proportional to the apparent extract, not the true final extract, because the solution now contains alcohol in addition to the original water.
 
My last 3-4 beers all had the same yeast safale 05 and they all settled at 1.025 using the refractometer. I am trying to figure out if I have a issue or is my reading off using the refractometer for FG. I don't have a hydrometer currently but that would solve my problem.
 
sodbuster said:
My last 3-4 beers all had the same yeast safale 05 and they all settled at 1.025 using the refractometer. I am trying to figure out if I have a issue or is my reading off using the refractometer for FG. I don't have a hydrometer currently but that would solve my problem.
Click to expand...
Refractometers do not read correctly in the presence of alcohol. Spend the money, get a cheap hydrometer. Get one like this one.

https://www.ritebrew.com/product-p/863021.htm
 
brewSJ said:
ABV
Click to expand...


i got a proof tralles hydro, for measuring a mix of pure water alcohol mixtures.....


but yeah they measure, density for volume weight displaced...(and now i'm wondering about living at 4500ft?)

:mug:

edit: damn, now i want to talk mols.... lol even better!
 
Last edited:
sodbuster said:
using a refractometer for both OG and final
Click to expand...
Aha. Then I would contend that my image from Terrill above is most accurate, and your ABV is in reality approximately 7.1%. Your FG is not, in fact, 1.026, but rather about 1.009. Using the old equation then, (OG - FG) * 131 = (1.065 - 1.009) * 131 = 7.3%. So it's in that ballpark from 7.1-7.3% ABV.

If your refractometer has an SG scale along with Brix, please do not use the SG scale. It leads to confusion, as we have seen in this thread. It is perhaps useful for OG readings, but not FG or ABV. Refractometers can only measure accurately in Brix, not SG. For final readings and ABV, use Terrill or Novotny to convert your final readings as I'd detailed previously, depending perhaps on whether attenuation is high (Terrill is more accurate) or relatively low (Novotny is instead more accurate). Your attenuation is probably about (65 - 9) / 65 = 86% = normal for US-05.

EDIT: I see now that we've been through all this once before -- thank you bracc for the old link from a few months ago.

Indeed... refractometers are handy and useful... but only if you use them correctly. And, as we see time and time again... they are not super easy for Joe Schmo to use correctly.
 
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if you ever do get a hydro, i want to know what it reads too.....because you can get a good guess about the ABV from the comparison ...
 
will do @bracconiere out of curiosity I will post readings from both instruments. Does anyone recommend a vessel to hold their hydrometer?
 
dmtaylor said:
Aha. Then I would contend that my image from Terrill above is most accurate, and your ABV is in reality approximately 7.1%. Your FG is not, in fact, 1.026, but rather about 1.009. Using the old equation then, (OG - FG) * 131 = (1.065 - 1.009) * 131 = 7.3%. So it's in that ballpark from 7.1-7.3% ABV.

If your refractometer has an SG scale along with Brix, please do not use the SG scale. It leads to confusion, as we have seen in this thread. It is perhaps useful for OG readings, but not FG or ABV. Refractometers can only measure accurately in Brix, not SG. For final readings and ABV, use Terrill or Novotny to convert your final readings as I'd detailed previously, depending perhaps on whether attenuation is high (Terrill is more accurate) or relatively low (Novotny is instead more accurate). Your attenuation is probably about (65 - 9) / 65 = 86% = normal for US-05.

EDIT: I see now that we've been through all this once before -- thank you bracc for the old link from a few months ago.

Indeed... refractometers are handy and useful... but only if you use them correctly. And, as we see time and time again... they are not super easy for Joe Schmo to use correctly.
Click to expand...

Thanks for the great info @dmtaylor
 
NSMikeD said:
you would think, I have seen side by side comparisons using tilt, hydrometer and refractometer and the tilt was the most reliable. Remember you need to adjust for temperature. And for the self correcting devices, they correct less effectively the further they move along the temp range for which they were designed. Also, you need to calibrate your devices.



lastly, it's all irrelevant anyway. IMO, most readings from home brewers are inaccurate (just take a look at how many post on the subject don't read a hydrometers meniscus correctly ). Unless you are dealing with a stuck fermentation or dialing in some advanced fermentation techniques, and you know exactly what pH and ions were on your water, the numbers aren't really going to make much of a difference. You'll still drink and enjoy your beer, and you'll likely never be able to tell by taste if your beer was a few points off (and perhaps even better than designed.

Fwiw (I have an iSpindel). If you calibrate your Tilt correctly. and it doesn't get stuck on Krause, it's nice to know when fermentation is leveled off without having to let O2 get to your beer. My refractometer lets me take quick reading but I only care about being in the ballpark. And my hydrometer is useful for double checking the other two (when I talk the time to cool wort/beer down to 60°

Keep leaning about gravity reading techniques and devices. It's good to know, and reducing user error will make your day more relaxing.

RDWHHB
Click to expand...
You consistenly get the same the same readings from your tilt vs a hydrometer?
 
sodbuster said:
You consistenly get the same the same readings from your tilt vs a hydrometer?
Click to expand...
You weren't asking ME, but... in my experience, it depends greatly on the amount of schmutz that gets stuck to the Tilt. For a few fermentations, somehow my Tilt managed to stay clean the whole time. In those instances, it matches a standard hydrometer within a point or two.
 
dmtaylor said:
You weren't asking ME, but... in my experience, it depends greatly on the amount of schmutz that gets stuck to the Tilt. For a few fermentations, somehow my Tilt managed to stay clean the whole time. In those instances, it matches a standard hydrometer within a point or two.
Click to expand...
Copy that. I think I will stick with the hydro for consistent results. though the tilt sounds like a fun tool to play with.
 
bracconiere said:
so SOB, POSs melt and leak on me....

https://www.ebay.com/itm/2557632190...cRaXPN5z/mGOGSXN+nElQKTWph4=|tkp:BFBMkvKWvLJh
is what you want for the hydro....


and as far as a hydro....

brewing america i think makes a triple set i can;t find....that would give you 1.0001 accuracy :mug:
Click to expand...
If I had a glass one I’d probably have gone through a couple by now, just like the hydrometers. I still use my OG (as in original gangsta!) hydrometer jar from 2004. I pull my boiling hot samples with a 1 cup Pyrex measuring cup, then it goes in the fridge. Works for me.

I can see how melting one would be a pita, though. To each his own. I just know I’m a klutz and if it’s breakable, I will find a way to break it.
 
sodbuster said:
You consistenly get the same the same readings from your tilt vs a hydrometer?
Click to expand...


I don't own a Tilt, I have a iSpindel. Don't go by me, I suck at taking gravity readings and I was a pre-pharmacy major decades ago. I am ok if things are in the ball park. My eyes and my tongue are my measuring instruments. I use BeerSmith and BeerFather software and use my municipal water report to give me an idea what all the numbers should be. If I am close I am ok.

I do however follow these type threads and I am always checking out the YouTube videos on the subject. I will see if I can find the link to the guy who did the three way side by side. I think the big surprise was the hydrometer was off, and while he was suspecting the Tilt would be unreliable it was the most reliable.

I don't use my iSpindel much. That's more for specialty fermentation jobs. I don't rush kegging (usually I give it two weeks in the fermentor and the air lock activity (and visual of the wort) let me know the yeast was healthy. I also don't brew high ABV beers that will test the limits of yeast, so I'm confident once I have good activity, the yeast will complete the job.

I usually will take readings with both the refractometer and the hydrometer after mashing to make sure they are close to each other and then just rely on the refractometer after that for convenience. and when you take your brix OG write it down. You'll need the actual number later on for the FG calculation. Beerfather is good at that. The calculator saves the actual brix number in the batch file for you.



editnnote. watch this

 
Last edited:
NSMikeD said:
you would think, I have seen side by side comparisons using tilt, hydrometer and refractometer and the tilt was the most reliable. Remember you need to adjust for temperature. And for the self correcting devices, they correct less effectively the further they move along the temp range for which they were designed. Also, you need to calibrate your devices.



lastly, it's all irrelevant anyway. IMO, most readings from home brewers are inaccurate (just take a look at how many post on the subject don't read a hydrometers meniscus correctly ). Unless you are dealing with a stuck fermentation or dialing in some advanced fermentation techniques, and you know exactly what pH and ions were on your water, the numbers aren't really going to make much of a difference. You'll still drink and enjoy your beer, and you'll likely never be able to tell by taste if your beer was a few points off (and perhaps even better than designed.

Fwiw (I have an iSpindel). If you calibrate your Tilt correctly. and it doesn't get stuck on Krause, it's nice to know when fermentation is leveled off without having to let O2 get to your beer. My refractometer lets me take quick reading but I only care about being in the ballpark. And my hydrometer is useful for double checking the other two (when I talk the time to cool wort/beer down to 60°

Keep leaning about gravity reading techniques and devices. It's good to know, and reducing user error will make your day more relaxing.

RDWHHB
Click to expand...
+1, They are estimates subject to instrument and random error. If you want to really geek out, take multiple measurements with each device, calculate means, standard error, and 95% confidence intervals. Too much fun and supports an illusion that you are a brewery scientist.
 
Last edited:
I guess I'll throw in my .02 -
I use my cheap ATC refractometer and Tilt hydrometer only for brewing all of my beers.
After learning how to properly use them, the refractometer and Tilt hydrometer readings are so close to my standard triple scale glass hydrometer that the difference is just noise.
I haven't used my triple scale hydrometer in years.
I use my refractometer during the initial brewing process for pre-boil and OG and the readings usually agree with BeerSmith unless I've done something wrong.
My Tilt OG agrees with my refractometer and is greatest thing going for keeping tabs during the fermentation process (especially lagers).
When Tilt says I've hit FG, I'll still let it sit for a few weeks before I crash and keg, and while kegging I'll take one last refractometer reading to make sure it agrees with Tilt and BeerSmith expected readings.
I never use the SG reading on the refractometer, only the Brix - and I use the BrewersFriend refractometer calculator (with a 1.04 WCF) to convert the readings.
I also did a manual 3-point calibrations on my two Tilt hydrometers.
 
OK side by side comparison the refractometer was reading 1.027 and the hydrometer read 1.025
 
Again, they are estimates. Take several readings, average, calculate standard deviation and look for statitistical difference. 2/100's of a point is not likely to be statisitically significant. How does the beer taste?
 
sodbuster said:
OK side by side comparison the refractometer was reading 1.027 and the hydrometer read 1.025
Click to expand...



this seems really weird, you said you had a OG of 1.065, right?

edit: i'm just saying aparently this liquid doesn't have much alcohol......


1675901603956.png



and that "corrected gravity" if what the OG would have been....
 
Last edited:
That’s is a cool calculator where did you find it @bracconiere? The refractometer reading OG was 15.9b and the hydrometer finished gravity was 1.025
 
Your readings cannot possibly all be correct. Have you calibrated your hydrometer and refractometer in plain room temperature water? Something isn't right.
 

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