Understanding MERV Ratings

The Minimum Efficiency Reporting Value (MERV) helps you compare different air filters for how effectively they trap particles like dust and pollen. This industry-standard rating can help you choose the air filter that’s best for your household. MERV ratings range from 1 for the lowest efficiency to 20 for the most efficient. Home heating, ventilation and air conditioning (HVAC) systems use filters rated from 8 through 13.

MERV ratings for home air filters

Check the owner’s manual for your home’s HVAC system or the manufacturer’s website to learn what air filters work with your HVAC unit. Most manufacturers recommend filters between 8 and 13 MERV for household use. Filters with ratings less than 8 don’t trap small particles, while filters with ratings greater than 13 are for commercial HVAC systems that are powerful enough to move air through the filter’s tiny mesh.

What do household air filters trap?

The MERV rating indicates the minimum percent of particles the filter removes in three size ranges. For comparison, a single strand of fine-textured hair is about 40 microns, and a grain of very fine sand is about 65 microns.

  • 0.3 to 1 microns is the tiniest particle size trapped. Particles in this range include tobacco smoke, bacteria and very fine pet dander.
  • 1 to 3 microns includes particles the size of lead dust and automobile emissions.
  • 3 to 10 microns includes large particles such as pollen, mold spores and aerosol mist.

The specifics for MERV ratings from 8 to 13

Air filters are rated based on the percent of particles they trap in each of the three size ranges listed above. Filters rated 8 or 9 don’t remove particles in the smallest group. Filters rated less than 8 only trap contaminants in the 3.0 to 10.0 microns range.

MERV 13: at least 50 percent of particles 0.3–1.0 microns; at least 85 percent particles 1.0–3.0 microns; and at least 90 percent of particles 3.0–10.0 microns

MERV 12: at least 35 percent of particles 0.3–1.0 microns; at least 80 percent particles 1.0–3.0 microns; and at least 90 percent of particles 3.0–10.0 microns

MERV 11: at least 20 percent of particles 0.3–1.0 microns; at least 65 percent particles 1.0–3.0 microns; and at least 85 percent of particles 3.0–10.0 microns

MERV 10: at least 50 percent particles 1.0–3.0 microns; and at least 80 percent of particles 3.0–10.0 microns

MERV 9: at least 35 percent particles 1.0–3.0 microns; and at least 75 percent of particles 3.0–10.0 microns

MERV 8: at least 20 percent of particles 1.0–3.0 microns; and at least 70 percent of particles 3.0–10.0 microns