If you want to know the exact alcohol content of your wine you will need to spend a few hundred dollars and purchase an Ebulliometer. If you are not a commercial winery, exact is not necessary. To obtain a ballpark idea of alcohol content, any of the many formulas or tables available to home winemakers will do.<?
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For those interested in yet another formula for calculating potential alcohol, I present the following for your entertainment and amusement. The formula is based on the work of Bryan Acton and Peter Duncan and is from their book <I style="mso-bidi-font-style: normal">Progressive Winemaking[/I]. This is the only formula I am aware of that makes the claim of being within plus or minus 0.5% of an Ebulliometer. This claim is for wines with an alcohol content of 10% to 14%.
ABV (Alcohol by Volume) = (OG – FG) / (7.75 – (3 * ((OG – FG – AG) / 800)))
Where:
OG = Original Specific Gravity times 1000 (i.e. 1.100 * 1000 = 1100)
FG = Final Specific Gravity times 1000
AG = Gravity adjustment. This is an adjustment to correct for the non-sugar solutes in the juice or wine. The authors state that the correction is usually between specific gravity 0.005 and 0.010. They recommend using 0.007. This number is also multiplied by 1000.
Example:
OG = 1100 (Original Specific Gravity of 1.100 * 1000)
FG = 1000 (Final Specific Gravity of 1.000 * 1000)
AG = 7 (the recommended 0.007 * 1000)
PA = (1100 – 1000) / (7.75 – (3 * ((1100 – 1000 -7) / 800)))
= (100) / (7.75 – (3* (93 / 800)))
= 100 / (7.75 – (3 * 0.116))
= 100 / (7.75 – 0.349)
= 100 / 7.40
= 13.51% ABV
If you repeat the above calculation with a final gravity of 0.990, the result will be 110 / 7.36 (Wade, does this denominator look familiar?) or 14.9% ABV.
I hope I got it right. Have fun!