May 11, 2017 – Reading Hydrometer

Crucial to the beer and wine making process is to know the sugar content of the beverage before fermentation, and the relative amount remaining after fermentation. This information allows us to approximate the amount of alcohol that can be created given the amount of sugars available for the yeast to consume, calculate the alcohol content in the finished product using an initial and final reading, and to ensure that fermentation is proceeding as planned.

Note that there are three different scales on a beer & wine hydrometer. Sp.Gr., which stands for specific gravity, is the scale all beer and wine kits purchased through Brew Your Own Brew will use.

To take a hydrometer reading, we’ll need the following items:

  • A Wine Thief
  • A Hydrometer Test Jar
  • A beer & wine hydrometer
  • A beverage to be sampled
  • A sanitizer of choice

After sanitizing all pieces of equipment, I like to start by placing my hydrometer into the hydrometer test jar. Holding the test jar on its side can help prevent the hydrometer from quickly dropping to the bottom of the test jar. Next, transfer liquid from the fermenter into the test jar using your wine thief until your hydrometer floats. Spinning the hydrometer helps to dislodge any air bubbles that may be stuck to the side of the hydrometer.
Keep in mind that water tends to stick to surfaces such as the glass hydrometer being used and forms a meniscus. Reading at the top of the meniscus will give you an inaccurate reading. Taking a reading based on the liquid level at the bottom of the meniscus will give you the most accurate reading possible.

It’s important to note that hydrometers are calibrated at a specific temperature, usually 60 degrees Fahrenheit, and should be listed on the hydrometer. For every 6.6 degree increase from 60 degrees, you must add 0.001 to the reading. For example, if my sample is at 72.4 degrees and my hydrometer reads 1.054 below the meniscus, the actual specific gravity is 1.056.

Checking the specific gravity of a beverage prior to adding yeast, called a starting gravity, and comparing this reading to the recipe will confirm that the correct sugar content has been reached, note that some deviation is acceptable. Remember to write this reading down in your brewing journal or on the recipe if you would like a final alcohol content.
Checking the specific gravity before transferring your beverage from your primary fermenter into your secondary fermenter will help insure that fermentation has completed. If you have not reached the final gravity stated on your recipe, corrective measures are more easily implemented in primary fermentation that in secondary. If this problem is not corrected, carbonation issues are much more likely to occur if you are naturally carbonating your beverage. If not carbonating your beverage, an improperly fermented beverage may be too sweet for your likings. If the reading closely resembles the final gravity stated on your recipe, you can confidently siphon your beverage into a secondary fermenter.


To calculate the alcohol content of your beverage, a starting gravity and final gravity are needed. First, start by subtracting the starting gravity by the final gravity. Then multiply this number by 131.25.
If I have a beer with a starting gravity of 1.056 and a final gravity of 1.012,
(1.056 – 1.012) = 0.046
(0.044)x(131.25) = 5.775
This tells us that the alcohol content in my beer is 5.8%

A hydrometer can be an invaluable tool in the beer, wine, and cider making process. Taking hydrometer readings throughout the fermentation process can help us insure that the product is ready to be moved from one fermentation vessel to another, or if corrective measures such as adding more yeast or nutrients are necessary to save the batch. These readings also tell us if the appropriate amount of sugar is available for the desired alcohol content and help us calculate a final percent.
As always, Brew Your Own Brew is here to help with any questions our customers may have. Feel free to call, email, or fax (should you desire), any of our three stores.

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