What do owners of fish tanks, home beer brewers, and auto experts all have in common? No, this isn’t a set up for a cheesy joke. These people — and many hobbyists and professionals — rely on a simple, inexpensive, but essential tool: namely, the refractometer. If you’re not familiar with the functions of a refractometer, it might be worth a refresher in some middle school physics.
The basic function of a refractometer is measuring the concentration of a substance in a liquid. This can be something like sugar in a glass of water or the amount of antifreeze in your engine’s coolant. The way a refractometer measures concentration is by gauging the way light refracts. When light enters a liquid, it bends at an angle. How much it bends depends in part on what’s in the liquid, and that’s where a refractometer comes in. You can use the index of refraction to figure out the concentration of whatever liquid you’re measuring.
One of the great things about a refractometer compared with other kinds of measuring tools is that it only requires a small amount of liquid. You only need to add a few drops of liquid to the measuring plate, rather than trying to fill up a vial like when using a hydrometer. The thing worth noting is that although most refractometers work the same way, they’re usually designed for use in a specific field. Measuring the salinity in a fish tank is a little different than measuring the gravity of a beer, and the scales on the refractometer reflect that.
We’ve rounded up a few different kinds of refractometers for different purposes, including home brewing, automotive maintenance, and even an option for beekeepers. These options rely on basic physics, rather than complex electronics. And even if you don’t totally get the physics of it, that’s okay. They’re easy enough to use. All you have to do is add a couple drops of liquid, point the end toward a light source, and look through the lens to see the concentration of whatever you’re measuring. These kits all include instructions on making sure the device is properly calibrated, too. And, since these devices are not actually electronics, you’ll never need to worry about changing batteries.
1. Salinity Refractometer for Aquariums
As is the case with most non-electronic refractometers, this option is inexpensive. This refractometer is designed specifically for use in aquariums, and the scale measures salinity. Much like a ruler with a centimeter and inch side, the scale on the viewer has dual measurements. You can gauge parts per thousand (0-100) or specific gravity (1.000-1.070). The kit comes with handy accessories, like a hard plastic carrying case for storage, a cleaning cloth, a screwdriver for making adjustments, and mini droppers. There’s also a user manual.
Pros: Great option for aquarium owners, comes with accessories like a portable storage case, a cleaning cloth, and mini pipettes.
Cons: May need frequent calibration.
2. Ade Advanced Optics Beer Wort and Wine Refractometer
Many professional breweries rely on refractometers for measuring the sugar content in the wort, and there’s no reason that homebrewers shouldn’t too. Wort is the liquid that is the precursor to the fermenting stage in the brewing process, and the refractometer will help ensure you have the brew you want. Many refractometers for beer, like this one, can also be used for making wine. This unit features two scales, one for the specific gravity of the wort and one for the Brix scale, which is the simple 1-100 scale that tells you the grams of sucrose in the solution. This kit, from Ade, includes a carrying case, a pipette, a manual, a cleaning cloth, and a screwdriver for making calibrations.
Pros: Dual scale for making easy conversions, includes bonus accessories like a pipette, a carrying case, a cleaning cloth, and a calibrating screwdriver. Includes automatic temperature compensation, allowing you to receive an accurate reading even with hot liquid.
Cons: Scale numbers are very small and can be hard to read.
3. Agriculture Solutions Salinity Refractometer for Seawater
Another solid option for fish tanks and other marine applications is this refractometer from Agriculture Solutions. It measures salinity, or how much salt is in the water. Like many of the other options on this list, this unit features a helpful dual scale, much like the inch and centimeter side of a ruler. While the dual scale will make the numbers harder to read, it does make it convenient to not have to do conversions. The two measurements provided by the scale are specific to gravity and parts per thousand. Included with the refractometer are accessories like a hard carrying case, droppers, a screwdriver, a manual, and a cleaning cloth.
Pros: Good option for marine applications and home fish tanks. Offers dual scale measurements. This refractometer is made from durable chromium. Comes with handy accessories like a screwdriver for calibration and droppers.
Cons: Calibration fluid will ensure an accurate reading, but it must be ordered separately, as this kit does not include the fluid.
4. Agriculture Solutions Antifreeze Refractometer
If you live in a cold climate, you’re probably well aware of the additional challenges cold weather poses to your automobile. Besides external problems like the difficulty of driving in snow, there are internal challenges like the havoc cold weather can wreak on the engine. Having a refractometer can help measure the freezing point of your coolant solution. The way it does that is by measuring additives like ethylene glycol and propylene glycol, depending on your antifreeze. This refractometer features both ethylene and propylene on the scale, and there’s also another scale for measuring battery acid.
Pros: Multi-use automotive refractometer can be used to measure a car’s antifreeze or battery acid.
Cons: Some auto refractometers feature an additional scale for measuring windshield wiper fluid, but this does not feature such a scale.
5. Robinair 75240 Coolant and Battery Refractometer
Making sure your car’s radiator is sufficiently prepared for cold weather is important, and a refractometer can be a good way to find out the freezing point of your engine’s coolant. It does that by measuring the level of antifreeze, whether it’s propylene glycol or ethylene glycol. This refractometer also features a scale for measuring battery fluid in electrolyte batteries. It’s worth keeping in mind what refractometers can and cannot do. They won’t be able to tell you things like the pH level of your coolant or provide any information on the additives in the antifreeze — it simply tells you the concentration of glycols, which can be handy in the event that you’ll be in extremely cold weather. This kit features the refractometer, a calibration screwdriver, a foam-lined plastic carrying case, and a cleaning cloth. There’s even a vial of distilled water to help you calibrate your refractometer.
Pros: Comes with a variety of helpful accessories like a foam-lined carrying case, a cleaning cloth, and a vial of distilled water to help you calibrate the refractometer. Unlike some other options, the refractometer has both Fahrenheit and Celsius scales for propylene and ethylene. There’s also a scale for battery acid.
Cons: More expensive than many of the other options.
6. Aichose Honey Refractometer for Honey Moisture
Not only is beekeeping a unique hobby, but it’s also a great way to help the environment by preserving nature’s most important pollinator. Not for nothing, it’s also a good way to make some extra money selling honey. One of the most important aspects in honey extraction is moisture content — the more water in honey, the sooner it will go bad. Beekeeping might not be as rewarding if you can’t keep your honey fresh, which is why a refractometer is a useful tool. The average honey refractometer features the Brix scale, which is the same scale used for beer and wine. This refractometer from aichose also features a 58-90% Brix scale, a water percentage scale, and the Baume scale. It also features automatic temperature compensation (ATC) for a more accurate readout.
Pros: Features 3-in-1 scales, including Brix, Baume, and water percentage for convenient readouts. Automatic temperature compensation for accurate reading even when using hot liquids. Includes all the necessary accessories.
Cons: Included instructions on calibrating the refractometer are lacking.
7. Brix Refractometer
Another convenient option for homebrewers is this affordable refractometer from Hobein. It features a dual scale — there’s 0-32% Brix and 1.000-1.130 specific gravity for wort. Necessary accessories like calibration screwdrivers, cleaning cloths, pipettes, and a carrying box are included. This listing also features various other refractometers, so you can get one for each of your needs. There are antifreeze, salinity, and honey options from the same brand.
Pros: Affordable, features a dual scale for measuring specific gravity and Brix.
Cons: Included calibration instructions are not very clear.