Alcoholmeter vs Hydrometer – What’s the difference for home distillation?!

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ByThe Brew Mechanic

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As you start on our brewing adventure, you are wondering what the heck are all these instruments?! From reflux still, jars to all the measuring instruments. Well my friend, alcoholmeter vs hydrometer gets mentioned a fair bit.

Guess what… it is pretty simple, we will break it down how each one works and what’s the main difference. Let’s get started. 

Differences between an alcoholmeter vs hydrometer?

Alcoholmeter has been calibrated to the density to measure alcohol (Ethanol) or proof of the liquid (ABV). The scale on the side of the meter only reads alcohol values and is smaller in length. This meter is calibrated at 20 Celsius by the manufacturer and should be reading at the correct temperature for accuracy. 

Hydrometer has been calibrated to the density of water and used in fermentation phases. The scale on the side reads the density of the liquid and is longer in size than the alcoholmeter. When calibrated between 15 to 20 Celsius by the manufacturer. 

Now we can see the difference between an alcoholmeter vs hydrometer, let’s dive into what they are.

Have fun testing out the alcoholmeter vs hydrometer for your knowledge as practice makes perfect. Enjoy team.

What is an Alcoholmeter?

With this meter, you can only measure the raw alcohol water mixture. This meter has been calibrated to the density and temperature of 20°C (68°F) of pure Ethanol.  The alcohol meter sinks into the liquid to a certain depth reading the actual alcohol water ratio. Showing the measured alcohol content as the proof of the liquid (ABV). It will show if the alcohol is  90%, 60% or 40% proof.

What is a Hydrometer?

A hydrometer has been calibrated to only measure the specific gravity (SG) of a liquid water mixture. In brewing a sugar wash solution density (SG) is measured to record the opening SG. At the end of fermentation, you again measure the final SG of the mixture. You then subtract the Open SG from the Final SG x factor to get to the potential alcohol you can expect from your batch.

This also helps you with making cuts. For more about the terminology, head to our distiller’s glossary.  

Can a hydrometer be used to measure alcohol ABV?

  •  In the initial phases of fermentation, a hydrometer is used to determine the potential alcohol you can expect from fermentation by density tests (SG). 
  • To measure the alcohol content (ABV) proof in your distilled spirit you will need an Alcoholmeter and not a hydrometer. 
  • To be put simply = No

How to Use an Alcoholmeter 

  • Wipe / clean rinse the test container/tube before using
  • Wipe clean rinse hands and alcoholmeter with alcohol if possible.
  • You should take the sample of alcohol at 20°C (68°F) to be accurate. 
  • Add the pure alcohol mixture slowly into the measuring tube creating no bubbles.
  • Add the alcoholmeter carefully into the measuring tube till almost full.
  • Spin the top section of the alcoholmeter a few times, make sure there are no bubbles present and the meter is in the middle of the test tube. 
  • Simply take the reading on the side of the meter to get the % (proof) pure, raw alcohol meniscus (curved surface area of the liquid) in the mixture. Reflux column distillate should be between 90 to 95% ABV.
  • When adding essences first get the proof of the alcohol correct by blending, say 40%. Then add the essence.
  • Why this is done? Essences added have traces of sugar, and flavouring in them and will give you an inaccurate proofreading. Especially the liquor essences.

How to use a hydrometer

  • The procedure is similar to testing the alcoholmeter
  • Wipe / clean rinse the test container/tube before using
  • Wipe clean rinse hands and hydrometer with alcohol if possible, clean water is fine.
  • The sample should be taken and measured it at 20°C (68°F) to be accurate.
  • Add the fermented mixture slowly into the measuring tube creating no bubbles.
  • Add the hydrometer carefully into the measuring tube till almost full.
  • Spin the top section of the hydrometer a few times, make sure there are no bubbles present, and the meter is in the middle of the test tube. 
  • Simply take the reading on the side of the meter at the meniscus (curved surface area of the liquid) to get the density (SG) of the liquid.

Example: How to dilute say 90% alcohol to 40% with an alcoholmeter

1. Take a sample of the concentrated alcohol with the alcoholmeter, and confirm it is 90%

2. Simple: Collect (5L) or the amount of raw alcohol you want to dilute.  X actual raw alcohol (90%) divided by the required concentration (40%) 

5L X 90% / 40%           = 11.25 Litres of water.
2.5l X 90% / 40%         = 5.6 litres of water.

The total volume of alcohol will now be the initial amount + added water @ 40% proof.

Note: Add 1 to 2 litres of water less, take a sample then adjust to be safe. Once you are confident then you can make accurate blends. You must still check the alcohol percentage % with the alcoholmeter after dilution to confirm the accurate reading. 

Let’s understand the difference

As The Brew Mechanic summarises this article, both the alcoholmeter and hydrometer are useful tools for DIY distillers, they serve different purposes. The alcoholmeter is used to measure the alcohol content of a raw alcohol-water mixture, while the hydrometer is used to measure the specific gravity of a liquid during fermentation. A hydrometer cannot be used to measure alcohol content in a distilled spirit, as an alcoholmeter is needed for this purpose. Have fun testing out the alcoholmeter vs hydrometer for your knowledge as practice makes perfect. Enjoy team.

Last Updated on July 10, 2023 by The Brew Mechanic

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With 35 years of knowledge of being a chemical engineer in alcohol manufacturing plants, my mission is to teach the next generation of home distilling alcohol brewers at a supernatural speed.

My reviews are based on real-life experiences with reflux stills, sugar wash, troubleshooting and mystical chemical reactions.

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