Everyone has been there. There’s a bad smell coming from the air conditioner. You open the air filter panel, and it’s covered with dust and dirt. It’s time to change the air filter.

But what kind of air filter do you need? What is a MERV rating and what does it have to do with air filters? Keep reading to learn what it is and which rating might be right for you.

merv rating

What Is a MERV Rating?

MERV stands for minimum efficiency reporting value. Air filters are made in such a way that some particles in the air, such as dust and pet hair, get through while others are stopped by the filter.


There are many types of air filters made of different materials and for different purposes. From the lowest quality filters to the highest medical-grade HEPA filters, they use the MERV scale.

The air filter MERV rating is a measure of not only the size of particles blocked by a filter but also what percentage of those particles get blocked. This typically depends on the material of the filter as well as how closely that material is stitched together.

The unit that typically represents the length in the MERV rating scale is the micron. A micron, or micrometer, is one thousand times smaller than a millimeter and is useful for measuring incredibly small objects.

What Do MERV Ratings Mean?

There are many different ratings that mean different things for air filters depending on what kinds of particles they block and how much of those particles. Different MERV filter ratings are useful for different environments and applications.

MERV 1-4

Air filters with a MERV rating of one through four are the least efficient at trapping airborne particles. They trap less than 20% of particles between 3 and 10 microns and are usually made from a mesh of aluminum or fiberglass.

These are able to trap particles like pollen; dust, including dust mites; and carpet fibers. However, they are unable to trap anything smaller than that. They are sometimes used in industrial settings for specific purposes.

MERV 5-8

The next category of air filters contains those rated 5-8. These typically filter out things like mold spores, hair spray, and furniture polish. These are on the cheaper side of home air filters, but sometimes they may not be enough.

MERV 5

Filters with a MERV rating of 5 block between 20% and 34% of particles between 3 and 10 microns. They are unable to block more than 20% of particles smaller than that.

MERV 6

Those with a MERV rating of 6 block between 35% and 49% of particles between 3 and 10 microns. They are also unable to block more than 20% of particles smaller than that.

MERV 7

Filters with a MERV rating of 7 block between 50% and 69% of particles between 3 and 10 microns. They are also unable to block more than 20% of particles smaller than that.

MERV 8

Those with a MERV rating of 8 block between 70% and 85% of particles between 3 and 10 microns. These are typically the lowest-end household air filters sold.

MERV 9-12

Air filters with a MERV rating between 9 and 12 are more typical of household air filters. They block things like pet dander, humidifier dust, and flour.

MERV 9

Air filters with a MERV rating of 9 block less than 50% of particles between 1 and 3 microns. They also block more than 85% of particles between 3 and 10 microns.

MERV 10

Those with a MERV rating of 10 block between 50% and 64% of particles between 1 and 3 microns. They also block more than 85% of particles between 3 and 10 microns.

MERV 11

Filters with a MERV rating of 11 block between 65% and 79% of particles between 1 and 3 microns. They also block more than 85% of particles between 3 and 10 microns.

MERV 12

Those with a MERV rating of 12 block between 80% and 89% of particles between 1 and 3 microns. They also block more than 90% of particles between 3 and 10 microns. These are the highest-end household box filters.

MERV 13-16

Air filters with a rating between 13 and 16 are used in commercial settings where air quality needs to be better than the average household. They block things like bacteria, smoke, and mucus droplets from a sneeze.

MERV 13

Air filters with a MERV rating of 13 block less than 75% of particles between 0.3 and 1 micron. They also block more than 90% of particles between 1 and 10 microns.

MERV 14

Those with a MERV rating of 14 block between 75% and 84% of particles between 0.3 and 1 micron. They also block more than 90% of particles between 1 and 10 microns.

MERV 15

Filters with a MERV rating of 15 block between 85% and 94% of particles between 0.3 and 1 micron. They also block more than 90% of particles between 1 and 10 microns.

MERV 16

Those with a MERV rating of 16 block more than 95% of particles between 0.3 and 1 micron. They also block more than 90% of particles between 1 and 10 microns.

MERV 17-20

This is the highest MERV rating for air filters on the market. They are able to block even the smallest airborne particles with great efficiency and are typically used in hospitals and cleanroom settings.

These filters block things like viruses and carbon dust and contain some of the best filtering technology such as HEPA and ULPA.

MERV 17

Air filters with a MERV rating of 17 block at least 99.97% of particles between 0.3 and 1 micron. They also block at least 99% of particles between 1 and 10 microns.

MERV 18

Those with a MERV rating of 18 block at least 99.997% of particles between 0.3 and 1 micron. They also block at least 99% of particles between 1 and 10 microns.

MERV 19

Filters with a MERV rating of 19 block at least 99.9997% of particles between 0.3 and 1 micron. They also block at least 99% of particles between 1 and 10 microns.

MERV 20

Those with a MERV rating of 20 block at least 99.99997% of particles between 0.3 and 1 micron. They also block at least 99% of particles between 1 and 10 microns. These are the gold standard for air filter technology.

Next Steps

Now that you know all about what a MERV rating means and how it impacts air filters, feel free to do some more research and find out which type of filter is best for you.

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