Determining Alcohol, Calories, and Carbs in your Homebrew

Posted on 01.08.08 5:30PM under Alcohol, Brewing, Calories and Carbs

Hydrometer SampleWhenever you make beer, by just taking a few simple measurements, you can determine the alcohol content and the calories in your homebrew. Many might be interested in alcohol content, and perhaps fewer in calories, but I personally enjoy knowing both of these things about my beer. Knowing that my Imperial Stout has 400 calories per bottle is one more reason to not overindulge, as they say. Besides, I’ve noticed a lot of search coming through asking things like “calories non-light beer” or “calories Guinness bud” or similar. So I figured people are interested in calories, and I gotta give the people what they want.

I will start with the executive summary, because I know you want answers. By measuring your starting gravity and finishing gravity with a hydrometer, you can easily determine your alcohol content. Calories are related to this alcohol content, but more related to the starting gravity – more sugar at the start makes for more calories at the end. Alcohol is slightly less caloric than sugar, but not by much. The equations are more complicated than I care to be bothered with, BeerSmith does the math for me. You can find the full math here. Carbs are pretty simple: take your final gravity, divide by four to get plato, and that’s the approximate number of carbs per 100ml of your beer. More info here.

All you need to get this information is your hydrometer. Chances are that whatever kit of startup equipment you bought came with one. If it didn’t, you should bookmark this page, stop reading right now, and go drive to your LHBS and buy one right now, or at least order one from your favorite online retailer. This is an essential tool. Brewing without one is like making coffee without measuring the beans. By taking an original specific gravity (OG) reading with your hydrometer, and a final specific gravity (FG) reading, you can calculate these important beery data points.

After you’re done boiling, you cool the wort and then strain it into your fermenter, where you aerate it somehow. After it is cooled and before it is aerated is the time to grab a sample for gravity measurement. Hydrometers work best at 60°F and although there is a temperature compensation table on all hydrometers, this compensation is notoriously inaccurate. I have never done an experiment myself to test the accuracy, but I tend to doubt it as well. So I always measure gravity in the 50-70°F range. That way it is off by no more than a point or two, which, if you’ve used hydrometers, you’ll know that it is easy to misread a point or two anyway. If you aerate the wort first, you’ll have tons of bubbles that may take hours to dissipate before you can get a good reading. It isn’t the end of the world, just a pain in the neck.

The hydrometer measures the concentration of sugar in the liquid sample. It doesn’t guarantee fermentability, but it does measure sugar content. You are on your own for determining fermentability. As I understand it, the theory of operation for a hydrometer is that sugar is denser than water, and so the more sugar in the water, the denser the whole solution is. The hydrometer is simply a calibrated weight, and so it sinks less in more dense water. That is why the numbers ascend as you go down the neck. The higher the float, the higher the gravity, the more sugar in solution.

Generally, the expected final alcohol content for your beer is one tenth of the OG. So if you started at 1.054, you might expect to end up with a beer of 5.4% alcohol by volume (ABV). Of course, there are many factors that go into determining how much sugar will be consumed by yeast and transformed to alcohol, but the 10% thing is a good rule of thumb. If you use half lactose or mash at 160°F, you might not get good attenuation, and if you use half corn sugar or mash at 140°F, you might get a lot of attenuation. By the way, attenuation just refers to how much sugar the yeast consumes and turns into alcohol. Low FG=high attenuation, high FG=low attenuation, got it?

The practical way to figure ABV (other than letting a computer program figure it out for you) is to subtract the potential alcohol at OG from the potential alcohol at FG. Both of these are read directly off the hydrometer.

The calorie calculation pretty much comes from the OG reading. As the FG drops, the calories will drop slightly, less than one calorie per point of gravity, but not significantly. So if you want to make a low-calorie beer, you must restrict your starting gravity and ensure a high attenuation. That’s why Bud Light, et. al. taste like nothing. They start with a low gravity, meaning there isn’t a lot of ingredients in there in the first place. They even need to use less hops to maintain the “balance” of flavor that is characteristic of the style. Then the beer is highly attenuated, leaving little residual sugar, and thus little flavor or character.

The truth is, that normal beer has like 200 calories or less per bottle, and you can make a pretty good lower calorie beer at about 150 calories per bottle, but is it really worth it to abandon most flavor to shoot for 100 calories? You’d have to hit OG 1.030 and FG 1.005. Why not just have one fewer beer?

Read Comments

  1. Posted by Bob Skilnik on 01.08.08 9:33 PM

    “The truth is, that normal beer has like 200 calories or less per bottle…”

    R-i-g-h-t. A normal beer.

    What the hell’s a “normal beer?”

    “That’s why Bud Light, et. al. taste like nothing. They start with a low gravity…”

    No they don’t. A-B starts with a high gravity beer and dilutes it down to meet their specs for a low-calorie/carb product.

  2. Posted by Keith Brainard on 01.08.08 11:07 PM

    Thanks for the comment, Bob Skilnik! I am often inspired by your relentless research in pursuit of accurate history and information. Thanks also for the link to your much deeper pursuits into the world of beer nutritional information.

    For a “normal” beer, I just went with my latest 5.6% ABV Stout, which ended up at about 200 calories per 12 ounces. I’m talking to homebrewers here. I think that most homebrewers make “normal” beer to be “normal” strength around 5%, and may make occasional big beers to be higher ABV than that. Maybe I’m totally off the mark there? At least that’s the way I brew.

    Diluting higher gravity beer is essentially the same as starting with a lower gravity, from a homebrewer’s perspective. In fact, that’s the most commonly advocated way of achieving target starting gravity. Practically all the extract brewing guides say something like, “dilute the cooled wort to your target gravity”. Similar principles are used in all-grain; many boil down to their target gravity.

    Of course, diluting as you describe makes a lot more sense than making low gravity wort from A-B’s perspective, as they can presumably make the same wort every time and then adjust it later in the process to create the desired product.

  3. Posted by Boak on 01.16.08 2:49 AM

    An interesting topic – I suspect I’m not the only person trying to combine a diet with a passion for beer.

    I’ve been assuming that a pint of beer with normal attenuation and 4.6% ABV is about 233 cal (That’s a UK pint by the way, 20fl oz). Various calorie counting websites give that as a broad picture. So for weaker beers, you assume a bit less, and stronger beers, you assume a bit more.

    But what if you have a beer with a lot of unfermentable sugars? Obviously, if it’s one you brewed yourself, you know the OG, but if it’s not, you really just have to guess.

  4. Posted by Keith Brainard on 01.16.08 8:04 AM

    A 20-ounce pint! Wow! That’s like practically two beers in one. I am mostly bottle-fed, so I think of “one beer” as a twelve-ounce bottle of 5% beer.

    You calorie number looks pretty accurate; maybe a little low, but close enough.

    Each point of starting gravity adds several calories, but even “a lot” of unfermentable sugars for most beer is probably only a few gravity points. That would amount to maybe a couple dozen calories – probably not a diet buster. Anything Imperial or Double and all bets are off, though. My Russian Imperial Stout is 10% ABV and boasts 442 calories per 16-ounce pint.

    As much as I try, it seems that it’s hard to take in more beer but leave calories lower.

  5. Posted by Kiwi on 04.30.08 9:12 PM

    Excellent summary for the determining factors, thanks! So my question is, your 10%ABV russian stout (sounds most excellent) got to that % by the recipe…which has more… sugars? and a better yeast? I am trying to up my alcohol %, but not ruin my homebrew.
    5% ‘Normal’ brew to a 10% is quite the leap!
    Any suggestions would be great.

  6. Posted by Keith Brainard on 05.01.08 8:50 PM

    It’s funny to look back at this, since I have a 100 calorie 3% beer that’s just about conditioned and I love it, though at the end of this post I basically said it can’t be done… how about that!

    Kiwi, I like your question, and I’m going to give it a post of it’s own.

  7. Posted by Brainard Brewing » Blog Archive » High Gravity Brewing on 05.01.08 9:26 PM

    […] wrote a post a while back about calories in beer. It was really fun to write, and even more exciting when Bob Skilnik called me out on a few […]

  8. Posted by caleb on 06.10.08 12:14 AM

    is there anyway to gage alcohol content without a starting gravity measurement? other than the old fashion drink-and-see method.

  9. Posted by Keith Brainard on 06.11.08 8:06 PM

    Hi Caleb

    I think you’d need a fancy scientific method to find the alcohol content of beer if you didn’t have a starting gravity. Something like weighing it, then heating it up to the point where the alcohol will evaporate but not the water, and then weighing it when all the alcohol was burned off. Then I bet you could calculate the alcohol by weight of the beer, and from that you could get to alcohol by volume.

    There may also be a very expensive instrument that you could provide a sample and it would analyze it for you.

    The other thing you could do, if you knew the recipe that produced the beer, is estimate a starting gravity, and that would get you in the ballpark of the alcohol content.

  10. Posted by Jbay on 10.27.08 10:53 AM

    How is it that in my search for calculations to determien %ABV, I have foudn several different calculations, some of whcih produce different valuew. In asking this, I want to mention that these various calculations all required starting and final gravities.

    Thanks

  11. Posted by Keith Brainard on 10.31.08 8:43 PM

    I can’t say that I am familiar with the calculation for ABV. I let BeerSmith do the work for me, based on OG and FG, as you mention.

    I do know that some of the measurement devices have an error caused by the fact that alcohol is lighter than water. This means that once the beer is fermented, its gravity will seem lower than it really is, because there’s a certain amount of the solution that’s alcohol, whereas the measurement device assumes water and sugar only.

    If you don’t have a BeerSmith or other program to tell you what your ABV is, then a decent rule of thumb is that your ABV is related to your OG. If your OG is 1.060, you might expect about 6% ABV. Similarly, if your OG is 1.080, you might expect about 8% ABV. It isn’t perfect, but it’s close enough for our homebrewing purposes.

    Hope that helps!

  12. Posted by Mike mishel on 10.31.08 11:33 PM

    How to calculate and know gravity to give a certain percentage alcohol

  13. Posted by Keith Brainard on 11.01.08 5:31 AM

    You have to measure gravity with an instrument. Normally homebrewers use a hydrometer or a refractometer.

    A hydrometer measures density based on weight. The amount that the hydrometer floats is proportional to the sugar density, and that is the gravity.

    A refractometer uses the refraction of light as it varies based on sugar density to give you a reading.

    Enough babbling… here’s an online tool for ABV calculating: http://www.rooftopbrew.net/abv.php

  14. Posted by Angelena peter on 02.05.09 1:52 PM

    W hile we all love the taste of beer, it’s the alcohol content thats responsible for beers standing in most societies. Its the alcohol content of beer that makes it the number one social lubricant.

    The alcohol content of beer is generally denoted by the “percent alcohol by volume”, or % ABV. “Percent alcohol by wieght”, % ABW, could also be used. It’s easy to convert between them. ABW = 0.8 × ABV.

    Beer’s alcohol content varies between about 3% ABV to about 12% ABV. However there are some outliers. “Low alcohol beer”, also known as “non-alcoholic beer” contains less than 1% ABV. The strongest beer ever made was the Hair of the Dog Brewing Company’s barley wine named “Dave”, which was 29% ABV.

    The type of beer plays a large role in the alcohol content. While it’s not exact, if you know the type of beer you can generally estimate how much alcohol you will be imbibing.

    This is an important skill to have. For instance if you go to a pub and all your friends are drinking pale ales, and you start ordering barleywines; if you try to keep up with them, you might not make it out of the pub without being carried. The following chart will help in these situations:
    ——————————————–
    Angelena Peter

  15. Posted by Bob Skilnik on 05.13.09 2:30 PM

    “non-alcoholic beer” contains less than 1% ABV”

    No, by federal standards, it must contain 1/2 of 1% or less.

    Low-alcohol and non-alcoholic beers and two different classes of beer.

  16. Posted by Better Home Brew Formula. | 7Wins.eu on 06.27.10 6:11 PM

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