What is the correct formula for calculating abv?

[Calder]

What is the correct formula for calculating abv?

I have used the following for a long time for beer:

ABV = (og – fg) * 131.25

However, I recently heard it is only accurate in the 5 to 6% range, and for higher alcohol, the following is more accurate:

ABV =(76.08 * (og-fg) / (1.775-og)) * (fg / 0.794)

Which is considered correct for wine?


There is significant difference at higher alcohol levels. Assuming an OG of 1.090 and an FG of 1.000:

ABV = (og – fg) * 131.25 =11.8%

ABV =(76.08 * (og-fg) / (1.775-og)) * (fg / 0.794) =12.6%

 

[DoctorCAD]

Statistically insignificant.

"About 12 or 13%" is close enough.

 

[JINKS]

What is the correct formula for calculating abv?

I have used the following for a long time for beer:

ABV = (og – fg) * 131.25

However, I recently heard it is only accurate in the 5 to 6% range, and for higher alcohol, the following is more accurate:

ABV =(76.08 * (og-fg) / (1.775-og)) * (fg / 0.794)

Which is considered correct for wine?


There is significant difference at higher alcohol levels. Assuming an OG of 1.090 and an FG of 1.000:

ABV = (og – fg) * 131.25 =11.8%

ABV =(76.08 * (og-fg) / (1.775-og)) * (fg / 0.794) =12.6%

I have a barley wine that shows 12.5% with the original formula and around 14.5% using the higher og formula.

1.124 og and 1.030 fg.

I discovered the discrepancy when brewcalcs said 14.3% and every other calculator had in the 12% range. @KidLightning supplied me with the second formula.
This is the post.

 

[Lebunim]

%ABV = Original SG - Final SG / 7,36 *1000

You can choose easy option and simply plot the numbers into this handy calculator

http://www.brewersfriend.com/abv-calculator/

 

[Calder]

%ABV = Original SG - Final SG / 7,36 *1000

You can choose easy option and simply plot the numbers into this handy calculator

http://www.brewersfriend.com/abv-calculator/

That is just multiplying by 1.32. The same as my first formula. I'm trying to figure out if that formula works for all gravities. Seems there is some disagreement. At higher gravities it could make a difference if you are reaching the limit of a yeast.

 

[Leithoa]

IMO for hobbyist purposes it doesn't particularly matter. Choosing one, or specifying the one you use is of more use. Both of these are estimates and as such not intended for any use beyond helping you make sure you don't accidentally get trashed on the strong stuff accidentally, or to help you troubleshoot your process.

Sure, they vary by 0.06-3.6% ABV over a range of 4.5-24%ABV but their divergence isn't strictly linear. It's nice to know exactly what the ABV is but again you don't need to know it unless you're selling it, and at that stage of the game your local regulations probably provide some insight on how they want it determined.

To that end here're some articles I came across trying to find an answer to the question.
This one shows the derivation of the two methods discussed originally
http://hbd.org/ensmingr/

Some more discussion but with a little more intro, it seems to be aimed at newer brewers
http://byo.com/american-amber-pale-...ion-extract-and-calories-advanced-homebrewing

This one has some interesting and involved (historical ?) methods for more accurate estimates and measures of ABV. The boiling one sounds like a good compromise, but it wastes 250mL of wine.
http://www.monashscientific.com.au/AlcoholDeterminationOtherMetods.htm

 

[FloppyKnockers]

I like the 1 beer plus 5 beers times 3 beers equals hugging the dog while he's laying on his dog bed and trying to remember lyrics to that one song from that one time but you can't because Taco Bell.

 

[Apple_Jacker]

If you have an Android phone, go to the Google Play store and search "Homebrew Calculator".