Hydrometer vs Refractometer: What’s The Difference?

Hydrometer vs Refractometer: What's The Difference?

Hydrometers and refractometers are both important tools used during the fermentation process. As such, they require regular and proper maintenance to ensure their accuracy. However, Hydrometer vs Refractometer, which is more accurate, what is the difference, and when should you use either?

A hydrometer and a refractometer are essential for measuring the alcohol content in beer where a hydrometer uses specific gravity while a refractometer uses the refraction of light, which is crucial for determining alcohol content and monitoring your fermentation’s health. Given that these devices monitor two separate but equally important factors during the fermentation process, it’s easy to see how there might be some confusion between them.

In the world of craft beer and other fermented beverages, home brewers and commercial producers alike rely on a variety of different tools to measure the potential alcohol content of their batches, monitor their progress over time, and ensure they’re meeting targeted standards.

Among these helpful measuring devices are hydrometers and refractometers. Both instruments are useful in different circumstances, but they measure different things. Knowing how each one works can help you make an informed decision about which one to use for your next home brewing session or professional brew day.

What is a Hydrometer?

A hydrometer is a device that measures the specific gravity or sugar content of fermented beverages. You can use a hydrometer to measure the sugar content of beer, wine, cider, and mead.

The hydrometer works by submerging it in a liquid and noting the reading on a scale at the bottom of the device. The higher the reading, the more sugar content in your beverage.

One downside to this method is that you’ll need to know what your original gravity was before adding yeast in order to calculate your final gravity.

At Hopsters Brewing Company, we have been using Triple Scale Alcohol Hydrometer for the last few years and recommend it for durability, accuracy, and having a complete kit for your measurements.

How does a hydrometer measure the alcohol content in beer?

How Does a Hydrometer Work?

A hydrometer is a device used in brewing to measure the specific gravity or sugar content of fermented drinks.

The device consists of a sealed glass tube that contains a weighted float.

When submerged in liquid, the float rises to the point where it matches the density or specific gravity of the liquid. The user then reads off the float’s position on the tube for an accurate measurement.

The device may thus be affected by the carbonation effect when used on a brew with a high temperature in addition to being fragile. One of the main challenges of using a hydrometer is that it requires a larger sample size which you can’t return to the brewing container.

What is a Refractometer?

A refractometer is a tool used to measure the sugar content of fermented beverages. It’s an optical instrument that uses light refraction to calculate the specific gravity or sugar content of a liquid.

A refractometer is typically used for making wine, mead, cider, and beer, as it can measure sugars dissolved in water.

The instrument is placed directly on top of the fluid to be tested and the user looks through the eyepiece to view a scale with lines denoting specific gravity or alcohol potential (%ABV).

As Hopsters Brewing Company, we employ both a refractometer and a hydrometer in our readings. This ensures that you get accurate readings to the satisfaction of the consumer.

Our recommended refractometer is Brix Refractometer with ATC. The dual-scale specific gravity measuring machine ensures that you have an accurate reading wherever you are brewing.

How Does a Refractometer Work?

A refractometer uses a special optical lens to measure the sugar content of a liquid by measuring the degree Brix. In reality, this measurement is actually the relative density of sugar and water in the liquid.

The more sugar in the liquid, the higher the density and therefore, the higher degree Brix. The refractometer is widely popular due to its simplicity, but it’s not very accurate at measuring specific gravity because it doesn’t take into account alcohol content.

This means that you’ll need to do some math to convert your readings. You also need to recalibrate your device after taking readings each time you use it so that you can get an accurate reading for future measurements.

Why should you use a refractometer?

Pros of Using a Hydrometer to Measure Sugar Content

A hydrometer is a tool that measures the specific gravity of a liquid and displays this measurement on a scale. The higher the number, the stronger the sugar content in a liquid.

Pros of using a hydrometer to measure sugar content are that it is inexpensive, easy to use, and highly accurate. Plus, it only takes seconds to get your reading with one of these tools among these other pros:

  • As compared to a refractometer, there is no need for calibration every time.
  • If you want to conduct a temperature correction, there are thermohydrometer models available on the market.
  • It is a high-quality device for measuring sugar content.

However, hydrometers are not designed for measuring the sugar content of beverages with a small sample; they’re pretty much only used for a lot of measuring liquids with a very high sugar content.

A typical homebrew will have an extremely high sugar content when first made but will eventually reach an equilibrium where there is no more sugar conversion happening. This means you’ll need to use different methods when converting sugars into alcohol during fermentation.

Pros of Using a Refractometer to Measure Sugar Content

A refractometer is an instrument used to measure the sugar content in an alcoholic beverage by analyzing the percentage of light passing through a wort or must.

A hydrometer, on the other hand, is a device that measures the specific gravity or density of a liquid based on how heavy or light it is. Refractometers are quick and easy to use and can be used on a small sample, making them ideal for homebrewers who want to perform fast measurements. Moreover, it is less fragile as compared to a hydrometer.

Moreover, the reading on a refractometer may not be affected by the carbonation effects of high temperatures as compared to a hydrometer.

Your sample only needs to be placed in the machine’s eyepiece and then you can read off your results immediately. Refractometers are also more accurate than hydrometers as they measure sugar content as opposed to density.

This means that if you have any residual sugars and alcohol leftover from fermentation, your refractometer will still be able to measure your sugar content correctly.

Cons of Using a Hydrometer to Measure Sugar Content

A hydrometer measures the gravity or sugar content of fermented beverages through a series of steps. First, you place a small amount of wort in a test tube and place the hydrometer in it to measure the specific gravity (°P).

The hydrometer will float at a certain point depending on the specific gravity. You then record where the hydrometer floats and what its reading is.

A refractometer is a simpler way to measure gravity because you just look through it and read the scale on top to see where it lines up. One major downside of using a hydrometer to measure specific gravity is that you have to wait for fermentation to complete before measuring it.

This means waiting until your beer has fermented for about two weeks before trying to determine whether your yeast has completed its job. If you don’t let fermentation run its course, then your hydrometer reading will be inaccurate and low even if your brew contains plenty of sugar.

This can leave you with an under-attenuated beer that tastes too sweet when you finally do drink it! It also takes longer than using a refractometer, which means more time spent away from brewing delicious beer.

Cons of Using a Refractometer to Measure Sugar Content

A downside of using a refractometer is that it can be difficult to measure the sugar content of beer with it. While this device can measure most of the sugars in wine, it cannot do so for beer because the different beers have different content which means you need to calibrate the equipment every time.

In fact, when measuring the sugar content of beer, you will only get a reading for the maltose. Additionally, while refractometers are great at measuring sugar content in wine, they can be tricky to use on distilled beverages like vodka and whiskey.

The reason? Alcohol changes the index of refraction, which causes readings to be inaccurate when using a refractometer.

Hydrometer vs Refractometer: Which is more accurate?

Hydrometer vs refractometer: Which is More Accurate?

Now that you have understood how each device works and its pros and cons, let’s explore which device is more accurate.

For beginners, we recommend getting a high-quality hydrometer because it does not require calibration and thus can be used easily.

However, it has several limitations for experts as indicated above. One of the main challenges with a hydrometer is the sample size required to make an accurate reading. It requires a bigger sample which you can not return to the brewing pot.

You can try using each device once you are a pro brewer or easily understand the working of the devices. Moreover, both devices require proper sanitation including sterilization or proper cleaning to ensure you do not include microbes as you are carrying out the specific gravity test.

Why Do You Need a Hydrometer or Refractometer?

When it comes to making wine, beer, or cider at home, you’ll need a hydrometer or refractometer to measure the sugar content of your fermented beverage. The devices measure the Specific Gravity, Brix, or degrees Plato to represent the alcohol content at any stage of the brewing process.

When you measure the specific gravity (or sugar content) of your alcoholic beverage, the measurement will tell you what percentage of alcohol is in the beverage. This can be helpful when you want to know how much alcohol is in a given batch so that you can adjust recipes according to your desired level of alcohol.

What time in the brewing process do you measure sugar content?

You should measure the sugar content pre-boil before adding yeast and starting the brewing process, post-boil to understand the sugar content before the fermentation starts, and before fermentation ends to understand the final beer alcohol content or sugar content.

Knowing the specific gravity (SG) of your wort before you boil it will help you calculate the amount of sugar needed for fermentation. Once your boil is finished, the SG of your beer will change since starch has been converted to sugar during the boil.

The SG can also change during fermentation, so don’t take a reading too early in fermentation and think you know what the final SG will be. Refractometers are used to measure the sugar content at any point during fermentation.

They are useful because they only require a few drops of liquid and work quickly, making them convenient for homebrewers who want to check the gravity throughout fermentation.

For example, if you want to know if fermentation is complete after one week, use a refractometer to test again after that time period has passed. The biggest difference between hydrometers and refractometers is that hydrometers measure gravity while refractometers measure Brix or degrees Brix (°Bx).

While both tools can be used to measure sugar content, hydrometers are more accurate when measuring gravity because they have their own built-in calibration scale.

For this reason, hydrometers are often used by professional brewers because they do not require calibrating each time before use like many refractometers do.

Final Words

No matter which measuring device you choose, it’s important to note that these devices do not actually measure the sugar content of your brew. They only tell you what the specific gravity or sugars are.

A hydrometer is a useful tool for homebrewers who are interested in how much sugar is in their fermented beverage, but it doesn’t tell them how much alcohol is there or how much yeast they need to add to achieve the desired level of alcohol.

A refractometer is a better option if you want to know the total amount of sugar and alcohol present in your homebrew.


What are the differences between a hydrometer and a refractometer?

A hydrometer is used for measuring the specific gravity of fermented beverages. It consists of a weighted float or heavy liquid (brandy) that is suspended in a long tube with markings to read specific gravity from. A refractometer is used for measuring the sugar content of fermented beverages. It consists of a magnifying lens, prism and scale to measure the degree Brix readings.

How does refractometer and hydrometer measurement device work?

The hydrometer is immersed into the fermented liquid, making sure it doesn’t hit any bubbles, and then removed quickly so it’s not swaying. This process causes some liquid to cling to the hydrometer and it’s read against the scales on the tube. The reading will be compared to tables included in the instructions or online at various brewing resources to determine sugar content level. Refractometers use light waves and require you first to use an alcohol solution on its surface to clean off any residue before taking your reading by simply inserting a sample into the lens area and looking through the eyepiece at scale on the back side of the instrument.

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