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July 27, 2023
Last updated

How to Measure Alcohol Content

Owner of Clawhammer Supply
how to measure alcohol content

There are several ways to measure alcohol content in beer, wine, cider, mead and spirits. In this article I’m going to show you four. Specifically, I’m going to show you how to use a hydrometer, a refractometer, a digital hydrometer, and a digital refractometer. And as a bonus i’m going to show you how to use a new equipment combination by Anton Paar to calculate alcohol content with a single measurement. If you’ve ever calculated ABV before, you’ll likely understand that this is actually a pretty big deal.

I've brewed a lot of beer and a bit of cider, mead and wine too. I've even tried my hand at making high proof fuel alcohol. One thing i've learned along the way is that knowing how to properly measure alcohol can be very helpful. I've made my fair share of mistakes, but I always try to never make the same mistake twice. In this article i'll try to give you the benefit of my years of experience by sharing all of my best tips and tricks as well as pointing out potential pitfalls.

Specific Gravity and Alcohol Overview

But before we get started, I want to quickly give you some background information so this all makes sense. In brewing we use changes in the density of liquid to determine alcohol content. Professional brewers use a scale called "Plato Gravity" to determine the amount of dissolved solids in liquid. Homebrewers typically use "specific gravity," which is the ratio of the density of a substance relative to the density of a standard. When using specific gravity to measure alcohol by volume, brewers are comparing the density of sugar water to the density of pure water.

The density of pure water has what is known as a specific gravity of 1. If you dissolve sugar in that water you increase its density and the specific gravity reading will be higher. If you then ferment that sugar and turn it into alcohol you decrease the density and the specific gravity will drop. If you take gravity measurements before and after fermentation you can use that information to calculate alcohol by volume or ABV.

Tools For Measuring Alcohol Content

alcohol content abv measuring tools

As far as measuring alcohol content goes, there are several tools that can be used to complete the job. The two primary tools are hydrometers and refractometers. Both are used to measure sugar content in an aqueous solution. Select the tool you're interested in for more information:

What Is a Hydrometer?

analog hydrometer

A Hydrometer is a scientific tool that we can use during brewing to determine how much alcohol was produced after a mash. It basically measures the density of liquid in relation to water.

There are 2 types of hydrometers:

A brewing hydrometer can be used to measure the specific gravity of high and medium gravity solutions. For example, you would use one of these to measure the starting and ending gravity of a wort or mash during the brew day and after fermentation.

A distilling hydrometer (also called a proofing hydrometer) is used to measure very low gravity solutions. For example you would use one of these to measure the proof of distilled spirits or the purity of fuel alcohol.

Commercial distillers making distilled spirits should own both a brewing hydrometer and a spirit or proofing hydrometer. A person or an entity making fuel alcohol would need both hydrometers as well. Commercial brewers or home brewers will only need a brewing hydrometer.

And to clarify, a brewing hydrometer cannot be used to measure the final proof of a distilled product and a spirit hydrometer cannot be used to measure the gravity of wort or finished beer. Read this article to learn more about the proper use of brewing hydrometers. And check this article for info on how a commercial distiller would use a proofing hydrometer.

What do Brewing Hydrometers Measure?

Hydrometers essentially measure the density of liquid. So, when brewing, the initial goal is to create a sugary solution that yeast will later eat and turn into alcohol. The more sugar that ends up in liquid, the more dense it will be. And the more dense the liquid is, the higher the brewing hydrometer will float in the liquid. This is the "original gravity" reading and it tells you the "potential alcohol" of a solution. I.e., using fermentation only (and not distilling), what is the maximum amount of alcohol you would expect to end up with after the yeast have done their thing. More on this below.

After fermentation is complete, you will use a hydrometer again to measure final gravity. As in, how good of the job did the yeast actually do? How much sugar did they eat and how much alcohol did they produce? The more sugar they ate and the more alcohol they produced, the lower the hydrometer will sit in the liquid. This is called the "final gravity" reading. Again, more on this below.

What do Distilling Hydrometers Measure?

Distilling or proofing hydrometers essentially do the same thing as brewing hydrometers. They tell the distiller how much alcohol is in a solution. However, the density of spirits and fuel alcohol is so low that a brewing hydrometer would sink right to the bottom. This is because alcohol is less dense than water. And much, much less dense than water with sugar in it.

So, distilling hydrometers are said to measure alcohol by volume or "proof." Fun fact "proof" is merely ABV multiplied by 2. For example, a 40% ABV solution of alcohol would be 80 proof.

How To Measure Alcohol Content With a Hydrometer

The process for measuring alcohol content using a hydrometer consists of the following steps:

  1. Measure Original Gravity
  2. Measure Final Gravity
  3. Calculate Alcohol Content (ABV)

Here's a video overview of entire process which also includes background information several tools that can be used to take the measurements:

Measure Original Gravity (For Brewing)

An original gravity reading is taken to determine how much sugar there is in the mash. This reading is taken BEFORE fermentation, just before yeast is added to the mash and it is aerated. As we mentioned above, the original gravity (OG) reading measures the amount of sugar in a liquid and roughly indicates the percentage of alcohol that can be expected in the wash, assuming that everything goes well during fermentation.

Using a hydrometer to determine mash original gravity

To use the hydrometer, fill a test tube or a tall glass with the liquid that will be fermented and drop the hydrometer in. Make sure it is floating and not resting on the bottom of the container. Hydrometers have a scale printed in or on their surface. The location at which this scale intersects the water will correspond with the specific gravity of the liquid. Taking the measurement is as easy as floating the hydrometer in the liquid and reading the number on its side.

OG varies depending on the recipe being used. For example, an India Pale Lager beer that we recently brewed had an original gravity of 1.055. If we use a yeast that ferments all the way down to 0.10, which is a common stopping point for brewers yeast, the ABV we will end up with is 5.91%

Write down the OG in your brewing journal, as you will most likely forget what it was by the time it is done fermenting, especially if you have multiple batches fermenting at the same time. Keep in mind that this reading alone does not tell you the alcohol content of your wash. It only tells you the potential alcohol content. You must take another reading (final gravity) and compare it to OG to determine the actual alcohol percentage of your wash, which we explain in the next section.

To reiterate, take an OG reading by completing the following steps:

  1. Use your beer sampler and fill your test jar almost to the top with liquid (you don't want any solids).
  2. Gently drop the beer/wine hydrometer into the test jar- you want to spin the hydrometer so it spins freely and does not stick to the side walls. You will see that the hydrometer floats on the liquid.
  3. Write down the number you see where the hydrometer intersects the liquid.

Measure Final Gravity

Using a hydrometer for moonshine mash

Final gravity measures liquid density, just like the original gravity reading does. However, if there weren't any hitches during the fermentation process, liquid density should be much lower because yeast ate all of the sugar (which increases density) and turned it into alcohol (lowering density). The difference between original and final gravity will tell you the alcohol percentage of the wash.

These steps assume your mash has been fermenting for at least a week and the activity in the airlock has slowed down significantly, if not stopped completely. If the airlock has not slowed down then wait a bit longer. Significant bubbling in the airlock means that the yeast is still working.

Once fermentation has finished, take a FG reading by completing the following steps:

  1. Use your beer sampler and fill your test jar almost to the top with liquid (you don't want any solids).
  2. Gently drop the beer/wine hydrometer into the test jar- you want to spin the hydrometer so it spins freely and does not stick to the side walls. You will see that the hydrometer floats on the liquid.
  3. Write down the number you see on the hydrometer- We are generally looking for a reading of around 1.010 or below. If the reading is above 1.010 let it sit for a few days and then take another reading, because the yeast might not be finished with their job yet. Keep taking samples over a few days until the reading does not change for 3 days in a row.

How To Read a Hydrometer- Temperature Correction

Most hydrometers are calibrated to be used at 60 degrees Fahrenheit. Check the instructions that came with it to be sure. If the liquid you are evaluating is above or below the calibration temp, you need to adjust for the actual reading. Again, this online calculator here offers help with the conversion

Calculate ABV (Manual Method)

If for some reason you can't access the online calculator we linked above, you can always calculate ABV manually. You need both the OG and the FG, mentioned above, to determine alcohol by volume (ABV). The sample we took for this article was at 1.055 and the mash fermented down to 1.010. Here's a simple math equation to determine the ABV:

  1. Subtract the Final Gravity from the Original Gravity
  2. Multiply by the difference between FG and OG by 131.

For example, the pictures used in this article were from a thin mash batch (corn whiskey that was boosted with some extra sugar). The OG was 1.090 and the FG was 1.010. Here's how to determine the alcohol percentage of the wash:

1.055 minus 1.010 equals 0.045.

0.045 X 131.25 = 5.91

Our beer is 5.9% ABV


How to Use a Proofing Hydrometer

A proofing hydrometer works (mechanically) exactly the same way a brewing hydrometer does. However, you don't need to take a "starting gravity" reading. Simply drop a distilling hydrometer in high proof alcohol and read the number on the side. It tells you proof / ABV directly without any calculation. Though there are a couple of caveats. First, just like a brewing hydrometer, a distilling hydrometer is "temperature sensitive" so you may need to correct for temp. Also, it won't accurately measure the proof of alcohol that has had sugar added after distillation.

What is a Refractometer

analog refractometer

A refractometer is a device that measures the concentration of a variety of substances dissolved in water by measuring how light is refracted, or bent, as it passes through the liquid. In brewing, refractometers are used to determine sugar content in an aqueous solution.

How to Use a Refractometer

The next tool we’re going to look at is a refractometer. My best advice is that before you use one of these, you actually just throw it in a trash can and get another tool, because these things are absolute garbage. I know i’m going to take heat in the comment section but I bet a lot of the people commenting actually have no idea how inaccurate these things are.

Wort Correction

The first problem with them is that they’re not designed to easily and accurately measure maltose, which is the primary sugar in beer. To use a refractometer for beer you need to build in a wort correction factor to account for the maltose, which literally requires plugging readings from 10 different mashes into a spreadsheet then using that information to correct all future measurements. Also, even if you have the patience for that, turbidity and the color of beer will still skew refractometer measurements as well and as far as I know there is no way to correct for that.

Temperature Correction

Hydrometers are also temperature sensitive and you need to correct for that as well. Always read the literature included with your hydrometer to determine how to correct for temperature.

Alcohol Correction

But the final straw with traditional refractometers is that they’re only good for measuring unfermented wort. You cannot use them to accurately measure liquid with alcohol in it either. So they’re useless when it comes to taking a final gravity measurement without using yet another spreadsheet and correction factor. If you’ve been using refractometers without doing all of this stuff, congratulations, your numbers were all wrong.

How to Use a Refractometer Correctly

However, if you’re dead set on using one of these, here’s how it’s done correctly. First, calibrate the unit by placing a few drops of distilled water onto the slide and setting the scale to zero. Next place a few drops of beer wort onto the slide, make sure there aren’t any bubbles, and hold it up to a light source. A natural light source is best. It likely won't be correct. To make this right apply a temperature correction and then a wort correction. Take these readings again once the beer is done and apply the same corrections as well as an alcohol correction, which by the way, still isn’t going to be very accurate.

Our buddy Brian over at Short Circuited brewing actually took the time to correct his refractometer using all of the steps described above. If you really want to use it correctly, follow the steps he outlined in his video on the topic.

EasyDens Digital Hydrometer

Ok, so let’s move on and talk about some of the newer, more high tech options. The first is the EasyDens digital hydrometer by Anton Paar.

EasyDens digital refractometer

The EasyDens measures brix, plato, and of course specific gravity as well as a bunch of other stuff. It’s accurate to .001 and is much easier to read than a standard hydrometer. Also, one of the really cool things about this is that it automatically corrects for temperature as long as your sample is in the ballpark of the calibration temp. And perhaps the best feature is that it only requires a tiny sample to get a reading, as opposed to an entire test tube. It’s a LOT more expensive than a glass hydrometer, but it’s a lot more convenient, it’s more accurate, and it’s much, much more convenient.

Setup is extremely easy. Just download the Brewmeister app for android or iphone, pop the EasyDens out of the box, hit power, and it connects automatically. Honestly, this is one of the easiest to connect and most reliable bluetooth devices i’ve ever owned.

To use it, take a small sample of wort, degas it with the syringe and run it through the unit. It’ll provide the temperature of the liquid and the temperature corrected specific gravity in a few seconds. To get the most accurate reading the temperature of the sample shoul be somewhere between 40 and 86 fahrenheit. If you want to use different units, just get into the settings on the app and navigate to what you want. You can also save the readings so you don’t even need to write anything down.

We’ve been using the first version of the EasyDens for years and this one is even better. It’s $400 bucks but if you’ve got the money, I highly recommend buying one. If not, I recommend adding this to your wishlist because it’s awesome.

SmartRef Digital Refractometer

The SmartRef digital refactometer, also made by Anton Paar, works like a standard refractometer, but unlike standard refractometers, it actually provides accurate numbers without the need for temperature and wort correction. That’s because the SmartRef has these calculations built into it. It can also measure the specific gravity of unfermented wort AND fermented wort because it has a correction factor built in for that as well. It’s also less expensive than the EasyDens.

SmartRef digital refractometer

To use it, download the brewmeister app, open the app, turn on the smart ref, and hit connect on your phone. Again, it connects automatically. Fill the cup to the line with wort and hit start. Note, this unit needs to be calibrated every now and again. To do so, fill it with distilled water, hit the little three dots in the upper righthand corner and choose the zero adjustment option.

At $269 dollars, the SmartRef is a bit cheaper than the EasyDens. It’s also very similar to the EasyDens but the EasyDens is a bit more accurate than the SmartRef. EasyDens also provides more measurement units.

Neither are cheap, but if this doesn’t bother you, i’d recommend the EasyDens. Also, if you’re a homebrew baller and money is no object when it comes to your hobbies, you might as well get both because if you do you’ll unlock a sweet feature that requires using the EasyDens and SmartRef simultaneously.

How to Calculate ABV with a Single Measurement

Using these units at the same time allows you to calculate the ABV of finished beer to within a half percent with no need for original gravity readings. That means you can just brew the beer and not take any readings and when it’s done you’ll still know the ABV.

Here’s a demo with some store bought beer. After grabbing a sample I’ll degas it with the syringe 4 or 5 times then fill both units and hit the “measure abv” button.

how to measure the abv of finished beer 1

As you can see, it more or less nailed the ABV of this pumpkin beer. Again, it only provides readings to within a half percent so it rounds, but i'll take it because this feature is sweet and i've never seen anything like this before.

how to measure abv of finished beer 2

Final Recommendations

If you're on a budget, we'd recommend purchasing a brewing hydrometer for beer, wine, mead and cider. We'd also recommend a proofing hydrometer for measuring the ABV of spirits. They're not the easiest to read and they require a lot more liquid (relatively) to get a reading, but when temperature corrected they're fairly accurate and the price can't be beat.

We recommend staying away from refractometers unless you're going to take the time to make all of the necessary corrections to the readings. Also, be advised that using refractometers to take all readings, including the final gravity (with an alcohol correction) will likely produce the least accurate results.

For those not on a tight budget, the answer is easy: we highly recommend the EasyDens. The SmartRef is great as well, but it's slightly less accurate than the EasyDens. That said, if you've got the money, buy both (buying the combo actually saves a bit of money). Using the EasyDens and SmartRef together to calculate the ABV of finished beer is pretty awesome!

Kyle Brown is the owner of Clawhammer Supply, a small scale distillation and brewing equipment company which he founded in 2009. His passion is teaching people about the many uses of distillation equipment as well as how to make beer at home. When he isn't brewing beer or writing about it, you can find him at his local gym or on the running trail.

  • I brew my mash n my final reading. The hydrominter went straight to the bottom . I couldn’t get a reading y ?

    Posted by JErr rAt on February 15, 2015
  • Question: Your article above suggested the ideal starting alcohol % is 5-8%. If the final age is higher, can you add water to the wash to get the desired 5-8 and get the same good results? Thanks, Jess

    Posted by Jess on December 17, 2014
  • The hydrometer is to measure the specifice gravity

    Posted by NME on May 23, 2014
  • how do u adjust specific gravity? I e I have a receipt that calls for a sg of 1.06, would u simply add more sugar to wash?

    Posted by tony harper on March 22, 2014
  • Cool Site. How much finished product will the government let you mafe for personal use?


    Posted by Shakey on February 26, 2014
  • Thanks for the info. I have a question, though. I use the Uncle Jesse’s recipe and method that I found of whereby you continue to remash the same grains, taking out a little of the spent corn each time and adding an equal amount of fresh along with sugar. Since there is some of the fermented wash left in the bottom of the bucket, doesn’t that affect the accuracy of the original SG reading?


    Posted by Walt on February 07, 2014
  • Do you sell hydrometers?

    Posted by local121 on February 07, 2014

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