Buying guide for best refractometers
![Eliza McGowen]()
Written by Eliza McGowen
Updated November 2021
A refractometer is an important tool for measuring the concentration of different liquids. Common in beer and wine making, this little device can take a small sample of liquid and measure the amount of refraction as light passes through. In doing so, this allows you to see how much sugar or other substances are within the liquid.
To find the right refractometer, you need to know why you want to use it. Different types have different designs and purposes. Using the wrong one means you won’t get accurate results. Once you know what you need, you can find the right refractometer for the job.
Key considerations
Refractometer vs. hydrometer
When you are measuring the specific gravity (the relative density of something compared to something else), it’s important to use the right tool, especially in practical applications like home brewing or aquatic upkeep. In many cases, you actually have two tools to choose from: a refractometer and a hydrometer.
Both tools can tell you the specific gravity given the liquid and its temperature which affects the final results. Hydrometers are a basic tool that measure the specific gravity by liquid displacement — the density is determined by measuring how much liquid is displaced. This method is quick, simple, and relatively inexpensive given the small cost of the tool. This makes it a great choice for beginning or budget-conscious users.
Refractometers determine density indirectly by measuring the amount of refraction of light through a liquid. Light bends when traveling through a dense liquid; the more density there is, the more the light bends. Compared to a hydrometer, a refractometer is more expensive but generally smaller, more accurate, and uses a smaller amount of liquid. This is a good pick if you want better measurement results.
Digital vs. analog
While all refractometers do the same job, some do so through digital or analog means. Analog refractometers are “old school,” reflecting light onto an eyepiece with measurement markings the user can see. Digital refractometers eliminate the eyepiece and use a digital sensor and readout instead, so the measurement appears as a clear number.
Analog refractometers are perfect for basic measurements, especially if you are looking for something inexpensive. The problem with the analog type, however, is the precision it requires for accurate results. The eyepiece can be difficult to read accurately since light can hit between the measurement marks. Positioning the sample on the refractometer can also be a chore if you are new to using one.
Digital refractometers offer more advantages, typically at a higher cost. The readout is easier to see, and with a higher resolution, the measurement is more detailed and accurate. Advanced features such as dual-scale readings, Bluetooth connectivity for smart devices, and waterproof ratings for lab use are also more common.
"Sometimes, liquids with a dark, non-transparent color can be difficult to read. A refractometer with a high sensitivity level will take better readings for these liquids. "
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Measurement scale
One challenging aspect when using a refractometer is learning the measurement scale the device uses for its readings. Since a refractometer measures the refraction of light instead of specific density directly, there is often some conversion required to make sense of the readings.
Many refractometers have a refractive index scale that measures how fast light travels through a specific liquid. This scale compares that speed with the typical velocity of light in a vacuum where there’s nothing to speed it up or slow it down.
A few models come with another or second scale, most often in Brix. This is a scale that measures the amount of sugar in a liquid. In homebrewing applications, this measurement is important to take in the wort (unfermented liquid, usually beer) before the fermentation stage to maintain accuracy and consistency.
Other refractometer applications use different scales. Some digital refractometers also allow you to switch between different scales.
Calibration requirements
Like any measurement device, refractometers must be calibrated to get the best, most accurate readings. There are several things that can affect the device’s accuracy, so calibration helps to cancel out certain factors ahead of time. Many models use a calibration liquid with known measurements to adjust the refractometer to deliver the same results.
Temperature is a common factor that can affect the final measurement results in nearly any refractometer. Many times, readings are taken after the liquid has reached room temperature. In some cases, the refractometer is calibrated to take a reading at the liquid’s temperature instead.
Refractometers with Automatic Temperature Compensation (ATC) can compensate for different temperatures and changes on the fly. ATC is a common feature on most home-use refractometers that eliminates the need to calibrate the refractometer to account for a liquid’s temperature. Instead, the ATC has a certain temperature range it can effectively correct, simplifying the process.
Features
Prism and sensor/eyepiece
A refractometer requires some way to direct and analyze light. This is done through some combination of a prism, eyepiece, or sensor inside the refractometer.
The prism bends light just like the liquid being measured, although with a different refraction index. The measurement is taken right at the point where the prism and liquid meet. If the liquid has a low concentration, the prism’s refraction index is higher. If the concentration is higher, the refraction index is lower.
Once the light passes through, it hits a point where the light can be measured. In analog refractometers, the light simply hits an eyepiece with measurement markings you can read with a quick glance. For digital refractometers, there is a small sensor that can read the light and produce a result.
Light source
For a refractometer to work, there needs to be a source of light that starts the whole process. Without the light, there is nothing to measure to determine the specific gravity of a liquid.
Most inexpensive and analog refractometers simply use the light in the surrounding environment. The refractometer has a small daylight plate that controls the amount of light allowed in. To work, you must hold the refractometer perpendicular to a light source and release the plate.
Higher-end, digital refractometers eliminate the need for a separate light source with a built-in LED light. Positioned on the opposite end of the sensor, the LED will turn on to start the refractometer’s automatic analysis process before the measurement is displayed on the readout.
Expert Tip
You can use distilled water to calibrate a refractometer with just a few drops sitting in room temperature.
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Refractometer prices
Refractometers vary in price, from inexpensive home-brew analog models to pricey digital refractometers meant for lab use. Under $100, most of your options are simple Brix refractometers meant for sugars/fruits in beer and wine making.
Moving up, it’s easy to find a reliable and easy-to-use refractometer for home use between $100 and $250. In this range, most of the options are either analog refractometers with an optic eyepiece or basic digital models with a specialized design (i.e. for home brewing).
Higher-end digital refractometers start at $250 and quickly go up towards the $500 mark with more features, better accuracy, a smaller build, etc. Many lab refractometers also soar past $1,000.
Did you know?
Some brewers use both a refractometer and hydrometer when checking the consistency of their wort to determine if both instruments are offering similar results.
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Tips
- Keep a refractometer stored in a clean, dry environment. This will keep the prism and sensor or eyepiece in good condition.
- If possible, store the refractometer in a place that has a consistent temperature throughout the day. Large temperature variations can mess with the longevity of the device over time.
- It’s important to clean a refractometer after each use. Otherwise, you risk getting the prism dirty.
- Refractometers without built-in scales can be difficult to use. Look for online scale converters to avoid having to deal with complicated formulas.
Other products we considered
Even though most home-use refractometers are geared for making beverages like beer and wine, there are plenty of refractometers for other uses. The Milwaukee Instruments MA887-BOX Digital Refractometer, for example, is a seawater refractometer with a digital sensor meant for marine use. The Hamh Optics & Tools 3-in-1 Refractometer has a more automotive-oriented focus for testing antifreeze and battery liquids.
FAQ
Q. Do I need a digital refractometer?
A. Digital refractometers do have a lot of benefits in terms of ease of use and accuracy, but a simple analog device can be just as handy. Analog refractometers offer a better value unless you have the budget for a higher-end digital version.
Q. How do I know if the refractometer is calibrated?
A. Several refractometers are based on a scale division equivalent to water. This means you can test the calibration by taking a quick sample reading of some water. For a Brix refractometer, the reading should be 0.0.
Q. Is a refractometer hard to use?
A. In most cases, a refractometer is simple to use. The most common design has you place a few drops of liquid onto the prism, point the refractometer to a light source (or turn on the built-in LED if available), and take a measurement.
