ABV Calculator

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DocWall46

Member
Does anyone know of an accurate ABV Calculator app (Android)? I have 2 separate ones and one just asks for my hydrometer readings, the other asks for temps of those readings, and the 2 calculations are around 1% off from one another.

BLL

Well-Known Member
ABV=(og-fg)*131.25

you don't need a whole app for that

Yooper

Ale's What Cures You!
Staff member
Mod
ABV=(og-fg)*131.25

you don't need a whole app for that
That's the formula I use. Easy, and fairly accurate. I'm lazy enough to leave off the .25 when I do it in my head.
I have a wine that started at 1.100, and finished at .992.

(1.100- .992) x 131 = 14.148 % ABV (14.1% is good enough for me)

or (1.100- .992) x 131.25= 14.175%

Either way is really close.

bernardsmith

Well-Known Member
Unless you are a commercial wine maker and are making wines and meads within certain ABV limits to avoid certain tax thresholds then expecting ABV calculations to be more accurate than 1% is a joke. You are dealing with a hydrometer that is fundamentally inaccurate; your own reading which will be inaccurate; and a calculator which is approximate. When someone claims that their wine or mead is 12.3% ABV I gotta laugh. It's 12%. anything more precise is simply wrong.

OP
D

DocWall46

Member
Good info. Thanks!

Just out of curiosity, do yall know how that formula came to be? Again just curious. Love learning stuff haha

fossilcat

Well-Known Member
Good info. Thanks!

Just out of curiosity, do yall know how that formula came to be? Again just curious. Love learning stuff haha
Here's the formula that I use in an Excel (Open Office) spread sheet:

=(((B1)-B2)*1.04678)/(0.0061773047+(0.78614031/B2))

B1 = the cell you enter the OG
B2 = the cell you enter the FG

I've attached the file I got this from.

But as bernardsmith points out, it seems silly to use all these decimal points when your hydrometer readings have such a large subjective factor. However, it's nice to know how things are "supposed" to be.

Attachments

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lschiavo

This space for rent.
I stuck the instruction sheet from my hydrometer on my fridge.

Take the difference between og and fg and read it off the chart. Was always close enough for me.

Gentle Jesus

Active Member
Unless you are a commercial wine maker and are making wines and meads within certain ABV limits to avoid certain tax thresholds then expecting ABV calculations to be more accurate than 1% is a joke. You are dealing with a hydrometer that is fundamentally inaccurate; your own reading which will be inaccurate; and a calculator which is approximate. When someone claims that their wine or mead is 12.3% ABV I gotta laugh. It's 12%. anything more precise is simply wrong.
Unless there is some error in the manufacturing of a (cheap) hygrometer which makes the thousandths place unreliable (ex.- O.G. = 1.065), I would be willing to give someone the benefit of the doubt that there wine was ≈ 12.3%. I think you can reasonably discern ±0.002 although maybe some people do not have the extra dash marks on their hygrometer.

cooper

Well-Known Member
Steve Fletty creates one that’s pretty good called BrewBot. I got the lite version which is free.

nickwhit9911

Member
That's the formula I use. Easy, and fairly accurate. I'm lazy enough to leave off the .25 when I do it in my head.
I have a wine that started at 1.100, and finished at .992.

(1.100- .992) x 131 = 14.148 % ABV (14.1% is good enough for me)

or (1.100- .992) x 131.25= 14.175%

Either way is really close.
How would you do a step feeding from 1.078 to 1.000 back to 1.020. back to 1.00 then up to 1.060?

Yooper

Ale's What Cures You!
Staff member
Mod
How would you do a step feeding from 1.078 to 1.000 back to 1.020. back to 1.00 then up to 1.060?
That'd be a super super high ABV, let's see, 78 points, plus 20 points plus 60 points. 158 points. So an OG of 1.158 and a FG of whatever it ended up with.

nickwhit9911

Member
That'd be a super super high ABV, let's see, 78 points, plus 20 points plus 60 points. 158 points. So an OG of 1.158 and a FG of whatever it ended up with.
It stopped when I did the last .060

nickwhit9911

Member
It stopped when I did the last .060
I used fletchman's bread yeast if that helps at all

Yooper

Ale's What Cures You!
Staff member
Mod
I used fletchman's bread yeast if that helps at all
It doesn't matter- the "points" are the same.

So you'd take the 1.158 OG and subtract the final gravity to get the ABV. If it stopped at 1.060 (good gosh that's SWEET!), you'd still just subtract it the same way, 1.158- 1.060 = 12.85% ABV.

nickwhit9911

Member
Awesome thank you so much

nickwhit9911

Member
It doesn't matter- the "points" are the same.

So you'd take the 1.158 OG and subtract the final gravity to get the ABV. If it stopped at 1.060 (good gosh that's SWEET!), you'd still just subtract it the same way, 1.158- 1.060 = 12.85% ABV.
It ended up a little bit sweeter then I had plans for but it is good surprisingly

Brooothru

Well-Known Member
Unless you are a commercial wine maker and are making wines and meads within certain ABV limits to avoid certain tax thresholds then expecting ABV calculations to be more accurate than 1% is a joke. You are dealing with a hydrometer that is fundamentally inaccurate; your own reading which will be inaccurate; and a calculator which is approximate. When someone claims that their wine or mead is 12.3% ABV I gotta laugh. It's 12%. anything more precise is simply wrong.
So then are you making an argument in favor of refractometers? Granted, FG readings are susceptible to computational errors to an extent, but refractive indices are subject only to the physics of light transmission (corrected to .10 degree of brix).

Pappers_

Moderator
Staff member
Mod
Add me to the list of those who round to the nearest whole number for ABV. We're not sending this stuff out to a lab for analysis LOL.

Brooothru

Well-Known Member
Add me to the list of those who round to the nearest whole number for ABV. We're not sending this stuff out to a lab for analysis LOL.
You mean me and my tasting bro' have to put away our lab coats??

Yooper

Ale's What Cures You!
Staff member
Mod
So then are you making an argument in favor of refractometers? Granted, FG readings are susceptible to computational errors to an extent, but refractive indices are subject only to the physics of light transmission (corrected to .10 degree of brix).
I won't speak for @bernardsmith but remember that refractometers measure the refraction of light in a sucrose solution, and once alcohol is in the mix, it skews the refraction of that light, so any refractometer readings are done by using alcohol correction software, and are thus even more subject to computational errors.

Brooothru

Well-Known Member
I won't speak for @bernardsmith but remember that refractometers measure the refraction of light in a sucrose solution, and once alcohol is in the mix, it skews the refraction of that light, so any refractometer readings are done by using alcohol correction software, and are thus even more subject to computational errors.
Well, yes and no. A BRIX refractometer measures the refractive index of the specific sugar sucrose. By applying a refractive index correction factor, the measured R.I. correctly measures the maltose sugar fraction. I would argue, it is significantly more accurate than interpreting where the meniscus of a hydrometer sample crosses the marker on a hydrometer. The R.I. is also less subject to temperature induced errors, and is easier to accurately read. The reading of Original Gravity would seem to be much more accurate when using a refractometer.

Now regarding Final Gravity (or any reading between O.G and F.G.) I agree that the presence of alcohol makes an accurate determination more difficult but not less accurate when the empirical application of corrective factors (not the visual observation and interpretation of those observations) is where potential errors are introduced.

The formulae for accurately accounting for these factors have been established to compensate for these variables, certainly to the accuracy needs of us in the homebrew community. After running many parallel measurements using both a calibrated refractometer and narrow band hydrometer (0.980-1.010 S.G), I have greater confidence in an R.I. index corrected for alcohol than the fidelity of a hydrometer corrected for temperature and human error or seeing the meniscus.

Brooo Brother