Honey refractometers measure moisture content

Honey refractometers are used by beekeepers and honey packers to measure the moisture content of honey. Technically, refractometers measure the refractive index of a substance.

Explanation: Light travels at different speeds through different materials. The refractive index is just a comparison between two numbers: the speed of light through a vacuum and the speed of light through the material you are testing—in this case honey.

Light also changes direction after it passes through different materials. If you measure the difference between the angle of incidence (light coming in) and the angle of refraction (light coming out) of a substance you can use this number to determine the refractive index. This is how a refractometer actually works.

Explanation: If you look at a straw in a glass of water you will see it looks distorted. This is because light moves faster through just the glass than it does through the glass and the water combined. Likewise, light will move faster through honey that has few solids than it will move through honey that has many solids. In other words, the refractive index of honey will change based on the amount of solids (sugars and other substances) in it.

Refractometers also make corrections based on temperature, because the refractive index will change slightly as the temperature changes.

Now, to make this all the more perplexing, the amount of solids in a liquid is measured on a scale called the Brix scale.

Explanation: Brix is a scary sounding name for a simple kind of scale. Each degree of Brix equals 1 percent sugar. So, grape juice with a Brix of 18 is 18 percent sugar. The Brix of honey can be from about 70 to 88.

Now here is where confusion sets in. While most refractometers give a reading in Brix (solids in water), honey refractometers give readings of water in honey. This is (kind of) the opposite of Brix.

Explanation: This type of reading is used in honey refractometers so beekeepers don’t have to subtract the Brix reading from 100 to get the moisture level. It’s just a convenience. However, it can get really confusing when a beekeeper uses a refractometer designed for another purpose—such as brewing. Not only are these designed to be most accurate in other ranges, the readings are in Brix—not 100 minus Brix. It it best to use a refractometer designed for your specific purpose.

Once you understand how a honey refractometer works, it is simple to use. There are many variations in design, but these are the basic steps:

  • Calibrate the device with distilled or deionized water
  • Put a drop of honey on the prism
  • Close the trap door that flattens the specimen
  • Focus the eyepiece
  • Read the scale

Two things are especially important for getting accurate results:

  • Make sure the container of honey from which your sample comes is well-mixed
  • Take multiple readings, and average the readings

Explanation: Honey is a variable product which differs from hive to hive, even from cell to cell. And honey that sits for a while will have a different moisture content at the surface than at the bottom. So before testing, always make sure the honey is thoroughly combined.

Human error also plays a part. Sometimes a reading goes awry for no apparent reason and sometimes the scales are just misread or misunderstood. To be on the safe side, multiple readings are always a good idea.

One last thing: read the directions. All these devices come with detailed instructions which should be followed to the letter.




Please tell us what is the role of moisture in honey???


The moisture content of honey must be about 16-18.5%. If the moisture is higher, the honey will ferment. If it is lower, the honey will crystallize.


Hi, Rusty, What can be done to avoid the extremes? Last year, my honey was above 18.5% and one suggested reason was from harvesting during the goldenrod season. The goldenrod has been around for about three weeks, or so, this year. Should I wait until it has stopped blooming? Chris



I don’t understand why harvesting during the goldenrod bloom would make any difference. If the honey is capped, it’s good to go and will be less than 18%. What reason did they give you for saying that?


He was just basing it on his experience that honey that had a large component of its source material from goldenrod could be too high in moisture. It sounds like you think that is unlikely.



The bees won’t cap honey until it is properly cured, no matter the source. So yes, I think it is unlikely. Perhaps the person accidentally extracted too many uncapped cells in with the capped ones. That would certainly shift the balance. The rule of thumb is never go over 10% uncapped, but I don’t like to cut it that close. I go for as few uncapped as possible.

That’s the most likely problem, but perhaps there were others. But like I said, the bees won’t get it wrong, just we humans.


I have an RHBN-90ATC refractometer that says use dioptric oil to calibrate it. I am having trouble finding dioptric oil; can any one tell me where to get it, please? I hve tried e-bay buy seem only to get kits with refractometer and oil; I just want the oil. Can I use anything else?


rusty impressive….but where can i source the best refractometers from


I recently went through purchasing a refractometer and after returning one I am going to keep the one from Blue Sky. It has only one scale that measures water in honey and that scale has 10 divisions between each whole percentage. I have been pleased with it.


Bud Perrin

When I try to measure moisture in honey on my handheld refractometer, there is no blue. What does that mean?



I don’t know; they are all slightly different. Did you read the directions?


Same here — I calibrated it according to instructions, put the honey on it, and the field is now white, with no blue. I’m wondering if I have the wrong kind of refractometer.


FYI, the scale in the display is 0-30 brix


I’m having the same issue. I think we’ve got the wrong refractometer. The scale is 0-30% Brix. I followed the instructions for calibration, and here’s why I think it’s the wrong kind of refractometer. Distilled water reads 0%, so it looks like I would be measuring sugar content with this scale — if it was a direct measure of water content, then distilled H2O should read 100%.

BTW – The only labeling I see on the refractometer are the initials ATC.


Yes you have the wrong refractometer. Brix is the percentage of sucrose in a solution so it is telling you the sugar content of the honey. The Brix number in honey should be around 82%. (82% sugar + 18% water).

Tom Andersen

Your meter is measuring below the Brix of the sample. I use a meter with a 58-90 range. You might be able to dilute the honey (by weight) with water (by weight), do a little math and get pretty close using your meter but you are probably better off getting the right meter. If you choose to use the dilution method, it might help to dilute a sample of honey of a known Brix, dilute and measure the result and use that dilution ratio as a guide to measuring your honey. A reloading scale is probably accurate enough to do this and can probably be borrowed if you don’t have one. Another way to get to the same point would be to accurately weigh a precise quantity of honey and do a little math or comparison with that. Honey weighs about 50% more than water (a pint of water is a pound, a pint of honey is about 1.5 pounds). If you go that route, watch the temperature and the meniscus to get a precise volume measurement (warm honey is going to be easier to get a volume measurement from).


How do I know the moisture content of a honey using refractometer?



A beam of light changes directions when it goes through different substances. Read the directions for your particular fractometer to learn how to use it.



Calibrate the device with distilled or deionized water.

Brad Bechthold

HI all,
So – one can essentially “measure” both Brix and water content (moisture), with a simple refractometer scaled for honey? Example – the moisture content is 17%, thus the Brix value is 83? Simple math?