How to Use a Hyrdometer in 5 Easy Steps

How to Use a Hyrdometer in 5 Easy Steps
November 19, 2019 Chase Ayres

When homebrewers are looking to take their brewing to the next level, it’s essential to learn about the chemistry of the brewing process. One tool that helps brewers deliver a consistent product is a hydrometer.

Content in This Guide:

What is a Hydrometer?

A hydrometer is one of many pieces of brewery equipment that a homebrewer will use when making beer. A hydrometer will allow the brewer to measure the amount of sugar content in their wort – the extract from the mashing process.

The hydrometer will measure at the beginning and the end of the fermentation cycle. This measurement will allow the brewer to calculate the amount of alcohol in the finished beer as well as approximate how well the yeast has performed. 

In brewing terms, a hydrometer will tell the brewer how well the yeast is turning sugar by volume. These readings will assist in knowing the state of the fermentation process.

Fermentation is a delicate process, and frequent readings will allow the brewer to make sure the fermentation process is going as planned.

How Do I Use a Hydrometer?

You can use a hydrometer in five simple steps:

Step 1: Sanitize your equipment

Some hydrometer kits will contain a “thief” that is used to remove a sample of the wort. Whether a thief or a substitute tool – like a turkey baster – is used to collect the sample, the devices must be sanitized to avoid cross-contamination.

Step 2: Fill the plastic tube that the hydrometer comes with

For reading to be accurate, the sample must be enough to make the hydrometer float within the sample jar. The sample might require using as much as 3/4 cups from the wort. 

The temperature will also affect the reading. The temperature should be within the range of your specific hydrometer.

Step 3: Place the hydrometer in the tube and let it settle

Once the sample is in the tube, add the hydrometer as well. Adding the hydrometer over a sink or other easy-to-clean area is recommended in case the tube overflows.

Spin the hydrometer, guarantee that it is not touching any of the walls of the tube. Touching the sides will produce an inaccurate reading.

Step 4: Read the hydrometer

Where the surface of the sample meets the surface of the air is the final measurement. 

Due to physics, the liquid will slightly curve up from where it touches the wall. Do not take the reading from the top of the edge. Instead, take a reading from the lowest level of the liquid surface.

Step 5: Discard the sample

The sample used to measure the specific gravity is no longer suitable. Adding the sample back into the wort will cause contamination. 

Tasting the sample is ok to get an idea of the final product, but discard the sample when finished.

Risk Involved With Inaccurate Hydrometer Readings

Using a hydrometer does come with risks. If the hydrometer reading is not correct, it is more challenging to know the state of fermentation of the brew. Inaccurate measurement will impact the final results of the beer.

If the reading of the hydrometer is off, it will also give an inaccurate reading of potential alcohol volume. The final product will have an unknown volume or a volume that is higher than it should be.

The most considerable impact of an inaccurate hydrometer measurement is the risk of contaminating the fermentation.  If the hydrometer is recalibrated, another sample is taken from the fermenter. The wort will then be exposed to potential contamination.

Hydrometer Temperature Correction Chart

A hydrometer gives an accurate reading when the wort is exactly 59 Fahrenheit. When the wort is at a different temperature, a calculation or table will correct the measurement.

The table below will provide an estimate, but there are also automatic calculators available online. 

Reference temp.Hydrometer reading kg/m³ or 10 ³ g/ml

20° C

(68° F) 


(59° F)

Temperature of liquid, °C



















0 +0.3+0.4+0.5+0.6+0.7+0.8+0.9+1.0

Hydrometer vs. Refractometer

A hydrometer is just one of the many tools available for measuring wort. A refractometer is another tool that measures the specific gravity of the beer.

Hydrometers and refractometers each have their pros and cons. The most significant positive for a hydrometer is cost. A hydrometer will provide a new brewer with a cheaper entry point for measuring than a refractometer.

A hydrometer will also allow for a more reliable measurement as the sample is more substantial. The accuracy of a measurement is better with a hydrometer as well. A refractometer may be out of calibration, but a calibrated hydrometer is less likely to go out of calibration.

The refractometer does have advantages over the hydrometer as well.

Refractometers require a smaller sample size, which leaves more wort in the solution and less risk for contamination.

Many refractometers come with automatic temperature correction making temperature less of an issue when testing samples.

Using a refractometer will also reduce the risk of contamination. Hydrometers will require the fermenter opened more to take the larger sample. A refractometer sample through the airlock, reducing the risk of contamination.

No tool used for measurement will be perfect. Both hydrometers and refractometers have their benefits and disadvantages. However, both will measure give accurate measurements when used correctly.

Best Hydrometers in 2019

There are many kits and hydrometers available on the market. Shopping for the best one can be overwhelming. Here are a few of the top hydrometers on the market:

1. Brewer’s Elite Hydrometer and Test Jar Combo

This hydrometer kit has a 4.5-star rating on Amazon with over 740 reviews. The kit comes with a triple scale hydrometer, 250ml test jar, storage case, cleaning cloth, bag, and brush. Graduated color bands on the hydrometer allow the brewer to know when the brew is ready. The triple scale hydrometer measures specific gravity, potential alcohol, and Brix balling. 

2. Master Distillers Hydrometer Test Jar

Another product with a high ranking Amazon review, this hydrometer has a 4.6-star review with over 100 reviews. This all-glass hydrometer set has no graduations on the cylinder, which makes for an easier to read product. The narrow one-inch diameter gives an accurate reading with a smaller sample. 

Other recommended hydrometers include:

Sodial Hydrometer for Home Brew Beer

Homebrew Guys Triple Scale Hydrometer Kit

Hydrometer Beer Wine & Glass Test Jar

As with any purchase, it is essential to do a test, read reviews, and do independent research before making a final decision.

Next Steps for Brewing Your Beer

A hydrometer is a tool that is used by professional and amateur brewers alike. For a homebrewer that is looking to advance their brewing skills, a hydrometer is a step in the right direction.

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