3 Reasons Why Your Starting Hydrometer Reading Is Wrong

His Starting Hydrometer Reading Is WrongTaking a starting hydrometer reading is one of the most important things you can do when making homemade wine. This is a reading that is taken with a wine hydrometer before the fermentation has started. It is usually taken at the same time the yeast is added to the wine must.

Having an accurate starting hydrometer reading will not only help you verify that you have an acceptable level of sugar in the wine must, it will allow you to determine the finished wine’s alcohol content. This can be done when the starting reading is compared to the finished reading.

The reading is taken on the Specific Gravity scale. This is a scale based on the weight of water. The weight of the wine is being compared to the weight of water. The more sugar in the wine must the heavier it will be. The more sugar in the wine, the more alcohol the yeast can make.

Keeping in mind its importance, here are the 3 reasons why your starting hydrometer reading is wrong. These are scenarios that I have run across more than once while helping beginning winemakers. In each of these 3 situations the hydrometer reading can be thrown off dramatically.

  1. Shop HydrometersToo Much Water Was Added: This mostly applies to individuals that are making wine from a wine ingredient kit. These kits typically include around 2 to 4 gallons of concentrate to make 6 gallons. The idea is for the winemaker to add water to make up the difference of the 6 gallons. But on rare occasions a beginning winemaker will add a total 6 gallons of water by mistake giving them an 8, 9, 10… gallon batch of wine. This in turn will give them a very low starting sugar reading on their hydrometer.
  1. Sugars Are Not Mixing Evenly: Before taking a starting hydrometer reading it is important to have the sugars completely dissolved and evenly dispersed throughout the wine must. This is regardless if it is from a concentrate or granulated cane sugar. Not doing so can cause your hydrometer sample to be non-representative of the entire batch. The result is an erroneous reading. For example, if the sugars are not completely dissolved and still hanging towards the bottom of the fermenter, the reading you get from a sample take from the top will be very different from the reading you get when taking a sample through a spigot at the bottom of the fermenter.
  1. Hydrometer Jar Not Being Used: One of the requirements for taking a starting hydrometer reading, is the hydrometer needs to be able to float. If the container being used to hold the sample isn’t tall enough, the hydrometer will sit on the bottom. Again, this will give you a wrong reading. This normally happens when the winemaker is trying to use the plastic tube the hydrometer came in to take the reading. This is something I strongly urge against for the simple fact it is not always tall enough to float the hydrometer. Instead, you should be using a hydrometer jar that is designed specifically for this purpose. It is more than tall enough and has a sturdy base so you can keep the wine sample steady and vertical while taking the reading.

These are by far the 3 most common reasons. If you think you have a starting hydrometer reading that is wrong, it is probably because of one of these three. There are other reasons as to why a hydrometer reading might not be completely accurate, such as not having your eye-level even with the surface of the wine, but these are the 3 “big ones”. Avoid doing them and you’ll be sure to have dependable readings.

17 thoughts on “3 Reasons Why Your Starting Hydrometer Reading Is Wrong

  1. I am 24 days in my 1st wine making attempt with a juice concentrate from a kit. I have used the hydrometer 3 times putting it straight into the fermenter. The readings are the same each time right around 1050. Is there something I may be doing wrong? I followed all instructions to a tee.

    • Dean, it doesn’t sound like you are having a problem with the hydrometer reading itself but may be experiencing a stuck or sluggish fermentation. I am providing you with the link to our article on the most common causes of fermentation failure. See if any of the reasons may apply to your situation.

      Top Ten Reasons For Fermentation Failure.

  2. I am new to wine making and noticed that my hydro readings read lower than what would be expected from the amount of sugar I put in. (When I tested my hydrometer it read about .046 to a gallon of water with one pound of sugar in it.) I suspect the sugar was not fully dissolved despite prolonged agitation and stirring. Is there a technique you recommend for making sure it is?


    • Tom, to ensure your sugar dissolves properly, we recommend dissolving it in warm water, let the water cool and then add it to the fermentation vessel.

  3. How do you compensate for water that is added after 1st reading at the beginning and before last reading before bottling?? Should a dilution adjustment be applied to one of the SG readings?
    I ask because often I will have up to 25% disagreement between SG calculations and Vinometer readings (even with a batch I have not diluted during the process). I know Vinometer will be inaccurate with higher alcohol wines, so I take Vinometer readings straight and diluted 50% with distilled water.

    • Yes for primary fermentation. Record degrees brix and record, then monitor fermentation. when it slows down, something less than 9 * change to hydrometer. You can look up the conversion to s.g. In a book or online!.

  4. No one has mentioned that Hydrometers come in different Temperature ratings. You are suppose to take the sample at that stated Temp. and they come with a compensation chart. I was sure you would have had this on your list.
    I used to use the container it came in, it was tall enough for sure but narrow and it always ” stuck” to the glass on the sides even though I would spin it ( no one mentioned this trick either) when I put it in the container.
    I bought a good Hydrometer testing container later on as I got better and never regretted it. Now it never sticks to the side .

  5. Hi,

    I freeze my fruit first to make them go mushy as recommended on this website, I then bash them a bit when making the must.

    My question is, if I take my hydrometer reading of my solution before adding the yeast, will some of the available sugar not be locked up in the cells of the fruit and not in the solution? This sugar then surely becomes available as the yeast breaks the fruit down during the primary fermentation….

    • Euan, while there is some sugar in the fruit pulp, the amount is so minimal that it will not make that much of a difference.

  6. I’ve tried two hydrometers and neither floats. I tested with water and it actually floated a tiny bit. I tested with store bought vodka, no floating. I’m not sure what’s wrong. I filled the testing container all the way and tried spinning it. Any ideas?

    • Jackie, if you are using a hydrometer meant for wine or beer making it will not work in vodka or any other type of distilled liquid. It is meant for use in wine and beer both. If you are trying to read the alcohol content in a distilled product, you need an alcohol hydrometer. If measuring distilled products, you will need the type of hydrometer listed in the link below.

      Alcohol Hydrometer

  7. Hello,
    I have an issue with my hydrometer reading. Trying to make a cider and after following all the relevant instructions I had my cider in a demijohn that already stopped fermenting. I tried the hydrometer reading and the specific gravity was around 1000. On the other 2 scales that should measure potential percent of alcoholic l and a sugar content, the reading was not even within the range of the scale (supposedly zero). What am I doing wrong? Is it that i dont read my hydrometer properly or i did not put enough sugar at the beginning?

    Thanks a lot!

    J. Kraus

    • A reading of .992 to .998 would indicate the that fermentation has completed. The potential alcohol scale should be reading 0% or less. This is because it is “potential” alcohol. It is telling your how much alcohol can be made with the sugars that are currently in the juice. It is not telling you how much alcohol is in the juice. Here is more on this:

      My Wine Hydrometer Is Reading No Alcohol Content

  8. How can the hydrometer be used to determine alcohol potential when the sugar is made in to a syrup and added three times as the Must converts to wine. Ref. Successful Wine Making At Home by H. E. Bravery
    Day one [in bucket]
    1. One quart of water with fruit
    2.1/3 sugar with 3 pints water
    3. Add yeast
    Day seven [transferred to carboy after straining off pulp]
    4. 1/3 sugar with 3 pints water
    Day Ten [transferred to second carboy]
    5. 1/3 sugar with 1 pint water

  9. day 1 after adding the sugar and water take a reading from the hydrometer (sp. gr. and potential alcohol) record both
    day 7 take another reading before adding sugar and water, record both, subtract the difference from day 1, let’s say you started with 1.100 sp. gr. approx. 12.5% potential alcohol on day 1, day 7 your reading is 1.010 sp. gr. and approx. 1.25% alcohol OK so now subtract 1.25% from 12.5% equals 11.25%. at this point you have 11.25% alcohol level in your wine juice.
    day 7 still you add sugar and stir in thoroughly, take a reading, record the reading, let’s say the reading is 1.020 Sp. gr. 2.6% potential alcohol, subtract 1.25% from 2.6%% equals 1.35% add this to the 11.25% equals 12.6% potential alcohol, do this also for day 10, after day 10 let the fermentation finish (no activity in the air lock) take a reading, if the reading is below 1.000 then the yeast has consumed all the sugar and the last recorded alcohol reading is what your % of alcohol level of your wine. kinda confusing you just have to write down and record. Have fun

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