Cart (0)

How To Determine Your Wine's Alcohol Level.

Posted on May 2, 2011 by Ed Kraus There have been 7 comment(s)

Alcohol In WineThis is the question every budding home wine maker wants to know, "How can I tell how much alcohol is in my wine?" The problem is, this question is usually asked about the time they're ready to bottle their wine.  Unfortunately, for the amateur winemaker, this is far to late in the process to make any accurate determinations.

What Needs To Happen
To know how much alcohol is in your wine, you need to take two readings with what's known as a gravity hydrometer. One reading is taken before the fermentation has started and the other reading is taken anytime after the fermentation has completed. By comparing these two hydrometer readings you can determine, with great accuracy, how much alcohol is in your wine.

Very simply put, a hydrometer is a long, sealed glass tube with a weight on one end. By observing how high or low it floats in a liquid you can determine a reading.

"And what are we reading?", you might be asking at this point. Essentially, we are trying to figure out how much sugar is in the wine or wine must. The higher the gravity hydrometer floats, the more sugar there is in the liquid, and the opposite holds true as well.

During a fermentation, sugar is what yeast turns into alcohol. If we know how much sugar there was in the wine must before the fermentation, and we know how much sugar there is in the wine after the fermentation, we then know how much sugar was consumed by the yeast during the fermentation. From this information we can determine how much alcohol is in the wine.

It all sound complicated when it is all explained in detail this way, but in practice it is very easy to accomplish. All you need to do is:

1. Take a gravity hydrometer reading at the same time you add the yeast to your wine must. The gravity hydrometer has a scale along it called "Potential Alcohol". At this point in the wine making process you should be getting a reading of around 10% to 13%. The reading is the point where the surface of the wine must crosses the scale. This reading indicates how much alcohol the wine can have if all the sugars are fermented. Write this number from the gravity hydrometer down and save it for later.

2. Take another reading with the gravity hydrometer once the fermentation has completed. This reading should be somewhere around +1 to -1 on the Potential Alcohol scale. By comparing these two gravity hydrometer readings you can determine your wine's alcohol level. Take the first number you wrote down and from that, subtract the second number.

The Calculations
As an example, if your reading before the fermentation was 12% and the reading after the fermentation was 1%, this means that your wine has 11% alcohol (12 minus 1). If your first reading was 12% and your second reading was -1%, that means your wine has 13% alcohol (12 minus -1).

Another way to think of it is you are monitoring how far along the gravity hydrometer's Potential Alcohol scale the fermentation is traveling. It started at 12 and end up at -1. That's' 13 points across the scale.

Further Information
You can find more information about using a hydrometer to make wine in the book, "First Steps In Winemaking." Also, the article, "Getting To Know Your Hydrometer" as lot additional information about using your hydrometer when making wine.
Ed Kraus is a 3rd generation home brewer/winemaker and has been an owner of E. C. Kraus since 1999. He has been helping individuals make better wine and beer for over 25 years.

This post was posted in Wine Making Blog

7 Responses to How To Determine Your Wine's Alcohol Level.

  • Jill
    Jill says:

    Dear E. C. Kraus,

    I always enjoy receiving your winemaking newsletter and read the whole thing. It contains a lot of good advice and winemaking tips, especially for beginners.

    This is why I was surprised to read the article in your June 7, 2011 newsletter, entitled "How to Determine Your Wine's Alcohol Level". When I was starting out in winemaking, I used the same procedure (subtracting to get the difference between initial and final Potential Alcohol readings) to determine the ABV because it seemed to make sense. With further experience and research I realized that simplistic approach is not accurate.

    The reason for the inaccuracy is that ethanol alcohol has an effect on a hydrometer. Sugar increases buoyancy and increases the hydrometer reading, but alcohol decreases buoyancy and therefore decreases the hydrometer reading. That is why a wine that has fermented to dryness has a negative Potential Alcohol or Brix reading instead of landing at zero (and a Specific Gravity below 1.000 instead of exactly at 1.000).

    Alcohol’s effect on a hydrometer may be much smaller than sugar’s, but it does have enough effect to throw off readings. If there is residual sugar, depending on the amounts the sugar and alcohol may actually cancel each other out, since each has an opposite effect on the reading. In other words, a Brix reading is never accurate once alcohol is present. One should never forget that what a hydrometer really measures is Specific Gravity.

    Fortunately, alcohol’s effect on hydrometer readings is predictable and can be calculated, and a few math-savvy winemaking authors have done so. A quick search of the Internet will give you this equation for a reasonably accurate way to determine the alcohol level of a wine:

    (Initial Specific Gravity - Ending Specific Gravity) x 132 = Percent Alcohol by Volume

    Some versions of the formula use 131 or 133 instead, but that does not impact the answer much. Also, there are formulas that use Brix instead of SG.

    Perhaps you are already aware of all this, but presented an inaccurate method in order to make determining the alcohol level simpler. Personally, I do not think that the above method is that difficult and I am all in favor of accuracy. Also, by having an accurate ABV it is then possible to go on and calculate the residual sugar amount (though that is slightly more complicated and also must take into account the presence of extract).

    If you are interested in more information (including the derivation of the above equation), a friend of mine has done quite a bit of research on the matter and his findings are posted on our winemaking club’s website Click on Winemaking Info to find articles he has written about potential alcohol, ABV and residual sugar.

    Again, thank you for the newsletter and for being a reliable source for quality winemaking supplies. Sorry that this response is a little late. I’ve been busy making wine!



    Posted on July 6, 2011 at 10:57 am

  • Don Faber
    Don Faber says:

    While not perfect, a good vinometer boasts being accurate to 1/2 percent. So, if you're not involved in some serious wine competition would this not suffice most amature wine makers. And if for some reason you didn't get a prefermentation hydrometer reading, wouldn't "close" be better than nothing? Just wondering!


    Posted on May 25, 2012 at 1:44 pm

  • Customer Service
    Customer Service says:

    Don, thank you for your great comment. The Vinometer is a somewhat accurate way to read alcohol levels in a finished wine. The biggest problem with them, and the reason we prefer the use of a hydrometer, is because they are not accurate at all with wines that have residual sugar left in them. The wine needs to be bone dry for an accurate reading. And for wines that are noticeably sweet, the readings are off the chart.

    Posted on May 29, 2012 at 8:07 am

  • Rick
    Rick says:

    I have been a scientist since I can remember (which is following the law of diminishing returns) and am puzzeled about people wanting to know accurately a wine's ETOH. As long as it is clear, takes great and has enough to keep the bugs out, do we really care?? Come on folks, give the poor yeast a break!

    Posted on October 25, 2012 at 1:05 pm

  • eibo
    eibo says:

    I think determining the amount of alcohol in a drink is fun, and important. You see, most people drink wine for one of two reasons, or the combination of the two. 1: taste and feel. 2: to get a buzz. Most people I present my wine to, when I tell them I've made it myself, ask how much alcohol is in it. For some reason they seem to be curious as to how I did it. Not sure why. If I can't answer that question, it seems to lessen my credibility as a winemaker. The world is a strange place!

    Posted on February 13, 2013 at 2:44 pm

  • Bob
    Bob says:

    Isn't it true that the readings obtained from the hydrometer must be adjusted depending on how much dilution occurred in the topping-off process? If I added a gallon of water to a 5 gallon carboy during the racking process, then the % alcohol will have to be adjusted, correct?

    Posted on March 7, 2013 at 11:52 am

  • Customer Service
    Customer Service says:

    Bob, your observation it correct. You can also think of it as adjusting for the alcohol or sugar left behind during a racking. You are replacing it with a liquid that has now alcohol or sugar... water. While technically sound, most people are not will to go through the math to figure such a minor adjustment. Hopefully, your topping-up volumes are much, much less than a gallon.

    Posted on March 8, 2013 at 6:25 am