Air Filter Guide: What MERV Rating Should You Use?

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When it comes time to replace your home’s air filter, it’s easy to get overwhelmed with all the different options available.

For instance, the last time I went to the hardware store there was an entire aisle that was dedicated to just air filters! That’s right—air filters in nearly every size, thickness, material, and MERV rating.

Today I’m going to talk about that last one—the MERV rating.

Depending on your situation, one MERV rating will be more appropriate than another.

Below I’ll discuss what to look out for when selecting an air filter and what MERV rating is best for your home.

What MERV rating should you use?

Since a high MERV rating means that more particulates will be removed from the air, you may think that air filters with the highest MERV rating are best.

However, a high MERV rating on an air filter usually means that the filter is thicker—your HVAC system will have to work harder to circulate air through your home.

When your HVAC system works harder, it uses more energy and experiences more wear and tear.

Using an air filter with a MERV rating of about 5 to 8 is appropriate for most residential homes.

MERV 5 – MERV 8 filters provide good filtration and will remove most pollen, mold spores, and dust mites.

Using MERV 5-8 filters will keep your HVAC system more efficient than using higher-rated filters, as long as you replace your filters regularly.

There are two main types of air filters: pleated and non-pleated. Generally, pleated filters have a higher MERV rating, while non-pleated filters have a lower one.

Quick Pick
MERV 8 Air Filters

With a MERV 8 rating and mesh-reinforced construction, these filters block most household particles. Since they come in almost any size, these are my favorite pleated air filters to use.

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Using an air filter with a MERV rating of about 10 to 12 is appropriate for filtration against allergens.

If you are susceptible to allergens, then you may want to use a filter with a MERV rating of about 10 to 12.

MERV 10 – MERV 12 air filters are able to trap particles as small as 1 micron such as automobile exhaust, pollen, and mold spores.

Sometimes particles such as pollen, pet dander, and fine dust are able to sneak by your filter unless you get one with a higher MERV rating. 

A filter with a MERV rating of around 10 to 12 is sufficient to remove most allergy-causing particles from your home’s air.

Most air filters that are able to remove common allergens will have the word “allergy” or “allergen” on their packaging. This is an indication that you’re on the right track.

Best Air Filters for Allergies
Filtrete Micro Allergen Air Filters

These MERV 11 filters will capture particles such as fine dust, pollen, and pet dander. Perfect to help prevent seasonal allergies.

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Some of the best air filters for allergies have extra features such as a carbon layer to remove odors. These are suited for people that have pets or other sources of smells in their homes.

One thing to keep in mind is that not all HVAC units are able to accommodate air filters with higher MERV ratings.

Some air filters, especially those with higher MERV ratings, may impede airflow due to enhanced air filtration.

Check out my article below on how MERV rating affects airflow for more information:

What is the best MERV rating to use?

Depending on your air filtration needs, there is a MERV filter that meets your requirements.

The table below shows the different MERV ratings and their typical uses as well as the typical material and shape that they are made of.

MERV rating comparison table

MERV Rating

Description

Application

Typical Air Filter Material

MERV-1 to MERV-4

Basic filter
Blocks carpet fibers and lint, but unable to block out much else.

  • Light Residential

  • Window/Split AC

  • Fiberglass

  • Washable aluminum

  • Synthetic mesh

MERV-5 to MERV-8

Typical filter
Blocks out common dust, pollen, and some mold spores.

  • Typical Residential

  • Typical Commercial

  • Pleated cotton

  • Polyester

MERV-9 to MERV-12

Better filter
Blocks out most mold spores, smog, fine dust, and pet dander.

  • Allergies

  • Better Residential

  • Better Commercial

  • Pleated cotton 

  • Microfine fiberglass

  • Usually 2" thick or more

MERV-13 to MERV-16

Superior filter
Blocks out bacteria, viruses, smoke, and other microscopic particles

  • Severe Allergies

  • Hospitals

  • Smoking Lounges

  • Pleated cotton 

  • Microfine fiberglass

  • Usually 4" thick or more

What is the MPR rating system?

The MPR rating system is an air filter rating system created by 3M.

The main difference between the MPR and MERV rating systems is that the MPR rating system is focused on a filter’s effectiveness at removing E1 microparticles from the air.

What is the FPR rating system?

The FPR rating system is a filter rating system that The Home Depot uses to rate air filters.

The main difference between the FPR and MERV rating systems is that the FPR rating system uses a scale of 1-10, while the MERV rating system uses a scale of 1-16.

For more information about the FPR rating system, check out my article below:

How does the MERV rating system work?

The MERV system is the industry-standard air filter rating system. It was established by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE).

ASHRAE standard 52.2 describes the methods and procedures for evaluating the performance of air filters as a function of particle size. In layman’s terms, it sets forth the minimum amount of particles that a filter must capture in order to obtain a specified MERV rating.

For instance, if an air filter can capture at least 20% of E1, 65% of E2, and 85% of E3 particles, then it will obtain a MERV 11 rating.

Air filter MERV rating specifications

The table below shows the minimum threshold that a filter must perform in order to obtain a specified MERV rating. As the MERV rating goes up, the filtration efficiency requirements get more stringent.

MERV rating parameters

Minimum % of particles removed by air filter

MERV Rating

E1 particles

(0.3 - 1.0 microns)

E2 particles

(1.0 - 3.0 microns)

E3 particles

(3.0 - 10.0 microns)

MERV-1

-

-

<20%

MERV-2

-

-

<20%

MERV-3

-

-

<20%

MERV-4

-

-

<20%

MERV-5

-

-

>20%

MERV-6

-

-

>35%

MERV-7

-

-

>50%

MERV-8

-

>20%

>70%

MERV-9

-

>35%

>75%

MERV-10

-

>50%

>80%

MERV-11

>20%

>65%

>85%

MERV-12

>35%

>80%

>90%

MERV-13

>50%

>85%

>90%

MERV-14

>75%

>90%

>95%

MERV-15

>85%

>90%

>95%

MERV-16

>95%

>95%

>95%

Higher-rated MERV filters must not only be able to filter out smaller particles but more of them as well.

It should also be noted that filters on the lower end of the MERV scale are not even tested for efficiency at capturing E1 and E2 particles. That doesn’t mean that they won’t capture any E1 or E2 particles – it just means that they aren’t proven to capture them at a specified level.

What are E1, E2, and E3 particles?

E1, E2, and E3 particles are particle range sizes that are used in testing air filters to determine a MERV rating.

Starting with E1, these are the smallest particles that are tested. E1 particles range in the size from 0.3 to 1.0 microns in diameter. Typical particles in this size range are smoke particles and bacteria. Only filters with a rating of MERV 11 or higher are tested with particles in this size range.

E2 particles range in the size from 1.0 to 3.0 microns. Typical E2 particles include pet dander and E. coli. PM2.5 are particles that are 2.5 microns or less in diameter, so the largest PM2.5 particles are considered E2 particles. Only filters with a rating of MERV 8 or higher are tested with particles in this size range.

E3 particles range in the size from 3.0 to 10.0 microns in diameter. Typical E3 particles include common dust, pollen, and mold spores. Most air filters are able to capture E3 particles to some degree. However, higher-rated MERV filters are able to capture more E3 particles than lower-rated ones.

What about washable air filters?

Washable air filters can be reused over and over again. They are usually made of metal or plastic and can be cleaned with water.

Washable air filters are great because you don’t need to spend money on disposable air filters. But the tradeoff is that you need to clean washable air filters more often.

For more information about washable air filters, check out my article below:

What you need to know when changing your air filter

If you are changing the air filter in your home’s HVAC unit, then you will generally need two pieces of information:

  1. Air filter size/dimensions
  2. Air filter MERV rating

Air filter size/dimensions

The size of your air filter can be determined by looking at the old air filter in your HVAC system. Most air filters have their dimensions printed right on them.

If you do not have an old filter to figure out the measurements from, then you can measure the dimensions of the filter holder in your HVAC equipment.

Filters are rectangular shaped, so there will be a length, width, and thickness (usually 1-2″ for residential HVAC systems).

how to measure an air filter

Air filter MERV rating

MERV stands for Minimum Efficiency Reporting Value. The MERV rating system is intended to be used to determine the filter’s ability to remove particulates from the air.

An air filter’s MERV rating is a scale from 1-16 that describes the minimum efficiency of the air filter. A low MERV rating means that the filter does not remove as many particulates from the air.

Conversely, a high MERV rating indicates that the filter does a good job of removing particulates from the air.

How often should you change your air filter?

Changing your air filter is necessary to maintain the health and efficiency of your home’s HVAC system. Anytime your use your AC or furnace, the air filter will get dirty as dust and particles flow through the system and accumulate on the filter.

The schedule that you will need to change your air filters depends on factors such as your home’s location, activity, and the presence of pets.

For most homes, the air filter should be changed every 1-3 months. However, you should check your air filter every month to see its condition and if it needs to be changed.

Activities such as home renovations, leaving doors to the outside open, and kids playing in the house can accelerate the accumulation of dust and particles on your air filter.

Which way does the air filter go in?

The air filter direction is important for proper HVAC unit operation.

Most air filters have an arrow marked on them to indicate the direction that the air is supposed to flow.

The arrow on the air filter should point to the blower, and point away from the return air duct.

If your air filter is in the return grille inside your home, then the arrow should point toward the wall or ceiling.

About Your HVAC Training Shop Author

Hi, my name is Trey Lewis and I’m the founder and chief editor at HVAC Training Shop. My goal for this website is to help homeowners troubleshoot and maintain their home’s HVAC systems. Whether it’s changing an air filter, troubleshooting a blower motor, or just buying a new humidifier, I want to make sure that you’re covered.