Is A Wine Refractometer A Good Alcohol Tester For Wine?

Refractometer With Grape Being SqueezedI have been told that a wine refractometer works real nice as an alcohol tester for my wine must and also at the end is this true?

Hello Gary,

Thanks for the great question. Testing the alcohol level of a wine is a subject that always seems to have some confusion among home winemakers.

A refractometer can not be used as an alcohol tester for wine. It will not test the alcohol level. A refractometer will only test the sugar level of a wine must or finished wine. This is no different than what a wine hydrometer can actually do. They both measure the sugar in a wine, not the alcohol.

By comparing two sugar level readings, one taken before the fermentation and another after, you can determine how much alcohol was made. This is because wine yeast consume sugar and turn some of it into alcohol. If you know how much sugar was consumed by the wine yeast, you can then determine how much alcohol was made.

This principal is exactly the same for a refractometer as it is for a hydrometer. Neither are alcohol testers, but they will allow you to calculate the alcohol level of a wine must or finished wine by comparing a current sugar reading (brix) with a beginning reading.

What makes the refractometer extremely useful — and more handy than a hydrometer in some cases — is that you can take accurate sugar readings with very small liquid samples — just a couple of drops is all that is needed. This makes it ideal for checking the ripeness of the grapes while out in the vineyard. You only need to squeeze the juice from a single grape to see how sweet the grapes are becoming. This is very valuable when trying to determine when to pick your grapesShop Refractometers.

Alternately, the hydrometer needs enough sample for it to float. This could take as much as 4 or 5 ounces of wine or must. A hydrometer jar is also needed to hold the sample. So as you can see more time and effort is involved to take a reading with a hydrometer. This pretty much rules out taking a sugar reading on the fly as you might with a refractometer.

Gary, to answer your question more directly, a refractometer is a great tool for any winemaker to have. It is very handy, and it provides a quick way to get a sugar reading almost anytime, anywhere. But a wine refractometer is not an alcohol tester. It will not directly give you the alcohol level of your wine. This can only be done by comparing a beginning reading (before fermentation) with a current reading.

Happy Wine Making,
Ed Kraus
Ed Kraus is a 3rd generation home brewer/winemaker and has been an owner of E. C. Kraus since 1999. He has been helping individuals make better wine and beer for over 25 years.

4 thoughts on “Is A Wine Refractometer A Good Alcohol Tester For Wine?

  1. Some constructive criticism:

    You stated in the newsletter ” A refractometer will only test the sugar level of a wine must or a finished wine”. This is an error….a refractometer will indeed test the sugar level in a must but not in a finished wine. As a matter of physics the hygrometer works on the principle of specific gravity whereas the refractometer operates on the principle of refracted light…a matter of pure density, not specific gravity. As useful as the refractometer is, once fermentation commences the refractometer cannot be used as the alcohol which is being produced has a much lower density than the other constituants of the wine. See this for yourselves by taking a specific gravity (hygrometer) reading on finished wine and then test the same wine with a refractometer. Big difference!

    Hope this helps.


  2. Ed, most commercial grape vine growers pick about 24 brix–which usually measures out to about 12-13% alcohol. In my experience and preference for sweeter wines, I do late harvest and, using my field refractometer, don’t pick grapes until they are about 26-28 brix or about 15-16% alcohol. Commercial growers add water to bring their higher brix levels down before bottling to make it more stable, drier and not subject to ABC taxes.

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