Are Hygrometers Accurate? (Explained)

by Alex Kountry
Updated on

Hygrometers are reliable and consistent instruments we use in several locations for measuring humidity levels.

Hygrometer accuracy is important in most cases especially when you are using it in sensitive areas.

Incorrect readings could lead to problems within a short period.

The accuracy levels of a hygrometer are often written on the instructions. Precision levels can range from RH ± 1 or 2%, 5%, 7% and 10%.

The accuracy of the instrument also depends on whether it is well calibrated.

This article will discuss the accuracy of hygrometers, how you can know if your hygrometer is accurate, whether cheap hygrometers are accurate, amongst other questions. 

Are Hygrometers Accurate?

Are Hygrometers Accurate

Having an accurate hygrometer is an important necessity for some uses.

Not everyone requires a top notch accurate hygrometer especially if it’s for basic use.

An accurate hygrometer is more important for greenhouse or cigar monitoring than for just using it around the house.

For example, using a hygrometer that presents wrong readings can lead to your cigars wilting or your plants getting sick from extreme humidity levels.

Even within the house, it is important for some individuals to be in humidity controlled environments. And for such people, accuracy in humidity readings is quite important.

Hygrometers are generally dependable and consistent instruments. Most are usually accurate to about 5% while some give precision levels of 1/2%.

Before buying the hygrometer check what the accuracy percentage says.

Also, ensure the device is well calibrated as calibration is an important factor that affects precision readings.

It is important to know that even if you bought the hygrometer with a 1 or 5% accuracy mark, you’ll need to recalibrate it over time.

This is because the sensors can get contaminated over time and this can affect the accuracy of your hygrometer reading.

How Do I Know if My Hygrometer is Accurate?

There are different ways you can use to check if your hygrometer is giving you correct readings.

Like I mentioned earlier, it is important that you are assured your hygrometer is accurate especially when your application is quite sensitive.

You can use calibration kits to check if your hygrometer is accurate. I would recommend the Boveda One-Step Calibration Kit for the job. It is very affordable and gets the job neatly.

However, you can also use a simple do-it-yourself test called the salt test with household materials. To carry out the test follow the outlined steps:

  • Get some salt, a Ziploc bag, a small cup and a liter of water.
  • Pour salt into the cup and add the water till it’s wet and feels like a paste. Ensure the water doesn’t dissolve the salt.
  • The cup should be placed in the bag. Add the  hygrometer beside. Zip the bag and place it away somewhere for 6 hours.  
  • Check the hygrometer after 6hours to see the humidity level. If the reading shows 75% then your hygrometer is accurate.
  • However, if the reading is either above or below 75% then the hygrometer is incorrect and you would have to calibrate it to read correctly.

The wet towel test is another simple method of determining hygrometer accuracy. It is particularly suited for analog hygrometers.

This test simply requires you to wet a hand towel and wrap it around the hygrometer.

Leave it on for 30 minutes. After 30 minutes, the humidity levels on the hygrometer should read 100%.

Any other reading aside that shows your hygrometer is not accurate and needs to be calibrated.

Here is an article I wrote on the importance of a hygrometer

Are Cheap Hygrometers Accurate?

Cheap hygrometers are often reliable instruments and are accurate to an extent.

Most cheap hygrometers fall within 5% and 7% accuracy levels.

This does not mean they cannot be higher than those. However, you cannot exactly test them until you have bought and are using them. 

A RH margin of 5% is relatively okay if you are not measuring a sensitive area.

However, you will need more precise devices for sensitive areas like for your wine cellar, greenhouse or cigar case readings.

Most cheap hygrometers are often basic and do not come with extra features such as remote monitoring or sending alerts.

Apart from the accuracy of the readings, these are other factors you might want to take into consideration when getting a model.

Being cheap does not equal inaccurate, however it might not be as advanced as the more expensive types. 

Is a Digital Hygrometer Accurate?

Digital hygrometers are usually very accurate with RH ± 1 or 2% and this level of accuracy is good enough even for sensitive applications.

Digital hygrometers as they come with various other options which the analog doesn’t have.

Digital hygrometers display their output with numbers which are easier to read and pinpoint than the analog ones which show the relative area on the needle.

They are also more advanced and some come with thermometer functions, ambient and dew point measurement.

The most interesting feature of the digital hygrometer is that it doesn’t have to be calibrated before it makes a reading.

Its inner functioning also guarantees a more accurate reading as it uses a thermistor to read humidity as opposed to the wet and dry system of analog hygrometers.

Also check out this article I wrote on the best hygrometer with data logger

Are Analog Hygrometers Accurate?

Analog hygrometers are also accurate and are still widely used by people. They are often cheaper and more basic than the digital models.

They need to be calibrated before they can be used. They can be factory calibrated or calibrated by the user. 

They are more versatile also and will get the job done easily. They are great for home and greenhouse use and are often accurate to ± 2% which is quite good.

They are also often used for measuring humidity levels in cigar cases. 

If you like to use the analog models then you have made a great choice as you will enjoy the simplicity.

They are however harder to maintain than the digital types but you do not have to worry about plugging them in or replacing batteries.

What is the Most Accurate Type of Hygrometer?

Dew point hygrometers are the most accurate type of hygrometers out there.

The most precise hygrometers are dew point hygrometers, which are generally used in locations where even the slightest amount of moisture is detected. 

The polished metal surface of these hygrometers is typical. Moisture condenses on the surface as humidity rises, and this is used to calculate current humidity.

Dew point hygrometers usually have a ± 1% accuracy.

This means they are often accurate to the mark. Most dew point hygrometers measure humidity, temperature and dew point together.

Some of them are weather stations, however, there are smaller models too which you can use within your house. 


The accuracy of a hygrometer is an important factor that you should take into consideration before getting a model.

The hygrometer can be accurate to a margin error of 1%, 2%, 5% or even 10%. The higher the percentage of margin error the lower the accuracy. 

To know if your hygrometer is accurate, you can carry out simple at home tests (salt test or towel test) or buy a calibration kit.

Cheap hygrometers are accurate to an extent however, their precision might not be as much of the more advanced and expensive models.

Both analog and digital hygrometers present accurate readings.

Digital hygrometers are slightly more accurate as they do not require calibration and use a thermistor to measure humidity levels.

Photo of author

About the author

Alex Kountry

Alex Kountry is the founder of HayFarmGuy and has been a backyard farmer for over 10 years. Since then he has decided to write helpful articles that will help you become a better backyard farmer and know what to do. He also loves to play tennis and read books


HayFarmGuy - Get Info About Farm Animals in Your Inbox