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Calibrating your thermometers and hydrometer

To begin this new year and makeing great beer we often for get some little things like calibrating our equipment. ow to calibrate a hydrometer - the easy way

A hydrometer used in homebrew and in professional wine making needs either very precise factory calibration (expensive!) or you need to calibrate it every time you use it. Fortunately, this is very simple so you can turn your standard homebrew hydrometer into a precision instrument with minimum hassle.

wine making hydrometer You can easily calibrate for most errors and use a low cost hydrometer to get a high quality reading using the following procedure:

Keep a trial jar with water near your brew. The idea is that this water have the same temperature as your brew so leave it there all the time.

Before using your hydrometer (every time!): Check the reading of the water. It should be around 1000 s.g. (0 on hydrometers showing oechsle degrees) but it will vary depending on temperature and scale errors.

If your hydrometer shows, say 1002 (+2) you obviously need to take your reading minus 2 to get it right. Then simply take all your wine/beer readings minus 2 and thats it!

Similarly of course, if your hydrometer shows 997 (-3) on the water - just add 3 to all your readings.

Remember that you have to check the water reading every time because temperature might have changed and/or your hydrometer scale might have moved inside the hydrometer. The beauty with this procedure is that it compensates for both temperature and scale moving errors at the same time so no need any more to make sure that the wine has a certain temperature before measuring the specific gravity.

Why do you need to calibrate the hydrometer?

There are many sources of errors when you use a hydrometer, either it is a cheap one or an expensive lab quality one.

Temperature: The same liquid will show different readings at different temperatures. High temperature means lower reading. Your hydrometer usually states what temperature to use it at (normally 15-20 C). If you have a liquid with another temperature there are formulas to calculate the correct value. But then of course you need an accurate thermometer as well.
Scale movement: The scale inside your hydrometer is usually glued inside to the glass and quite often the glue is not good enough which means it slides up or down.
Scale misplacement: In production, especially on cheap hydrometers, the scale might have been fitted in the wrong position. A more expensive hydrometer would probably have been tested in water before approval so you are less likely to have this problem the more money you spend on your hydrometer.
You can easily calibrate your hydrometer for all the above problems which means that you can use a low cost hydrometer and still get a high quality reading. Calibrating your hydrometer - here is how you do it.

Scale distortion: Scales are often photocopied from previous production run and eventually this might distort the scale. This is a less common problem and if it is there, it us usually very small, which is fortunate because we can not calibrate this error away (since it is
There are two methods for calibrating thermometers:

Ice point. Fill an insulated glass with crushed ice and then add a little water. Let it sit for at least five minutes and then insert the sensing part of the thermometer into the cup. Make sure the sensor is in the middle of the glass and at least an inch from the sides, bottom, and top of the glass. Hold it there for 30 seconds or until the dial stops moving or the digital thermometer beeps. Your thermometer should be reading 32 degrees Fahrenheit after 30 seconds. If it’s not, it needs to be recalibrated. The ice point method is the most accurate way to calibrate a thermometer.

Boiling point. Boil at least six inches of water. Once the water has reached a rolling boil, stick the sensor part of the thermometer into the middle of the water, taking care to keep it at least two inches from the sides, top, and bottom. After 30 seconds, the thermometer should read 212 degrees Fahrenheit if you’re at 1,000 feet or less of elevation. See below if you are at a higher altitude. If it doesn’t read 212, your thermometer needs to be recalibrated.

Changes in boiling point temperature by elevation:

Sea Level: 212 degrees Fahrenheit
1,000 feet: 210 degrees Fahrenheit
2,000 feet: 208 degrees Fahrenheit
3,000 feet: 206.4 degrees Fahrenheit
4,000 feet: 204.5 degrees Fahrenheit
5,000 feet: 202.75 degrees Fahrenheit
8,000 feet: 197.5 degrees Fahrenheit

How To Calibrate A Thermometer

Dial thermometers have a little screw or nut that adjusts the dial to the correct temperature. Simply turn the adjuster until the dial reads the correct temperature according to the method you’re using to calibrate.

Digital thermometers have a reset button. Simply push that button when you’re at the temperature point and your thermometer is ready to go.



Yes, this is a topic every one whom brews should pay close attention to! Bravo! Sneezles61

Of course the thermometer is important. Not so much your hydrometer IMO. If it’s off plus a point it will always be off a point so the end result will be the same no? Of course unless you use two different hydrometers

Yes Brew Cat, temp IS more critical, yet, trying to be accurate at any level of brewing, is a desirable goal, and an ongoing process. Sneezles61

I agree and Temp and volumes I try to be accurate. But the hydrometer is kind of a pita. I’ve broken mor than one and I have troubles reading them anyway. I’ve been thinking of getting a refractor but i hear people complain about them also.

Excellent. I pinned this topic.

You’ve been at this a long time, so if you have hit yer targets, within a point or two, then I would say, yes, you really don’t need to take readings or, better yet, be as concerned… Sneezles61

Oh I take readings. I’m just saying if I start at .050 and end at .010 or I read .054 and end at .014 I have ended at the same place. Therefore I don’t bother calibrating my hydrometer. Of course if I were off by .01 then I would check

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I urge you not to use the freezing/boiling method of thermometer calibration if you don’t have to. I’ve seen thermometers that were fine at boiling or freezing, but off at mash temps…unless you mash at freezing or boiling temps! The best way is to get a calibrated, certified lab thermometer and use that to calibrate your brewing thermometer.

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I do agree with you denny I too have seen that too. But having some point of calibration for cheap thermometers is better than none. I double check mine with my thermoworks that I have calibrate by them at the lab. The boil and freeze method does work just not as accurate as the lab. Here how to contact thermoworks for those interested getting thier thermometers done

Take two or three thermometers and check your mash temp. If they all read the same I’ll bet their good

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I don’t think I have ever seen 3 thermometers read the same temp. But if you had 3 reading the same than I agree your good. :grinning:

I use dials and they read the same. Maybe not down to the the decimal point but close enough for brewing beer

I had 3 different thermometers all read 208 in boiling water. I assumed a low pressure front moved in

I agree with Denny. I have a thermometer that I calibrated with both the ice and boil method and when I checked it at 170 degrees with a lab thermometer it was off by more than 10 degrees. Needless t say I don’t use it because I just don’t trust it. Went to digital after that. Id say if you plan on using a dial thermometer then calibrate with a lab thermometer in the temp range you will be using it at.

That’s different from my experience had troubles with all my digitals. Nothing but trouble. Went back to dials.

I have one of these when I checked it against the digital and dial on my MT the dial was accurate, the digital was off.

I have been using SensorPush Thermometer for 3 months.

It’s really simple, takes about 3 seconds to pair with your phone by just setting the sensor on top of your screen.
Works so much better than my old fashioned hydrometer, and does exactly what you would expect from a temperature and humidity sensor.

Thanks for this informative piece. I found out that has great thermometers and hygrometers and I did not know how to classify them. Thanks for this input I now know what to do.

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