MERV Rating Chart: MERV 8 vs 11 vs 13 for a Furnace Filter

By Ray Bennett · Updated 2 October 2026 · 5 min read · Checked against the sources at the end

MERV Rating Chart: MERV 8 vs 11 vs 13 for a Furnace Filter

Short answer

A MERV rating says how well a furnace or AC filter catches particles from 0.3 to 10 microns, and higher catches more. Trane recommends nothing below MERV 8, suggests MERV 11 for a house with pets, and MERV 13 for smoke or sensitive lungs. EPA says upgrade to at least MERV 13 or as high as your system's fan and filter slot can take, and not every system can take a 13.

A MERV rating tells you how well a furnace or air conditioner filter catches particles. EPA says the rating reports a filter’s ability to capture particles between 0.3 and 10 microns, from a test developed by ASHRAE, and that the higher the number, the better it traps them.

Higher is not automatically better for the machine, though. This page shows what each number catches, which one the makers suggest for which house, and when a better filter causes trouble.

Before you start

What to carry: a torch and a pen, to copy the size and the rating off the frame of the filter you have now. Five minutes.

Gas or electric? Either. Every forced air furnace, air handler and heat pump has a filter, and the rating means the same in all of them.

Know the slot. Trane says MERV 8, 11 and 13 all come in the standard one inch thickness and in thicker ones, and that a thicker filter lasts longer between changes. The slot decides which you can use.

What the makers are firm about. Not every system can take a MERV 13. Trane says a MERV 13 can restrict airflow and affect how the system performs, so check with your heating and cooling company first. Lennox says the same of 13 to 16.

No ozone. EPA says to avoid filters and air cleaners that intentionally produce ozone, a lung irritant.

A filter does not fix mold. EPA says filters do not deal with the cause of mold and musty smells. That is water or moisture, and it has to be found.

What the numbers mean

EPA's table as bars. Each figure is the least a filter at that rating catches, on average, in that size range.

Check 1

Read the rating against what you want to catch

MERV 8. Trane says it catches pollen, larger dust particles, dust mites, mold spores and lint, and may be enough for a house with no pets and no allergies, asthma or breathing problems.

MERV 11. Trane says it adds bacteria and fungi, pet dander, skin flakes and hair, and calls it the sweet spot for many homeowners. With pets it is the better choice over a MERV 8.

MERV 13. Trane says it adds viruses such as the flu, tobacco smoke, cooking smoke and smog, and suits a house with a smoker or someone with a breathing illness.

Below 8. Trane does not generally recommend anything under MERV 8. You can see through some fiberglass filters, and dirt builds up inside the system and the ducts.

Which one for your house

What Trane suggests for each kind of house, and the one question to ask before going to a MERV 13.

Check 2

Pick the highest your system can breathe through

EPA’s advice. If you upgrade, choose at least MERV 13, or as high a rating as your system fan and filter slot can take. EPA says a heating and cooling technician can tell you the highest that will work.

The usual range. American Standard says professionals generally recommend MERV 8 to 13 for a home, because the higher the rating, the more a filter can restrict airflow.

Lennox’s guide. MERV 6 to 8 for basic protection, 9 to 11 for moderate allergy control, and 13 or higher for sensitive people, if the system can handle it.

Allergies, smoke or wildfire. American Standard says use the highest rated filter suitable for your system when someone has allergies or a breathing condition, or when smog or wildfire smoke is a problem.

When a better filter causes trouble

Check 3Free to check

Watch the airflow after an upgrade

What goes wrong. Lennox says a filter rated higher than a system is built for can impede airflow, using more energy and wearing the system faster.

What it looks like. Weak air at the vents, a furnace shutting itself off on its limit switch, or an air conditioner coil icing up: a furnace limit switch and an AC freezing up.

The fix. Go back a step to a lower rating, or ask about a thicker filter cabinet. Trane says thicker filters come in the same ratings and last longer.

Getting the most from it

Check 4

Run it, check it, change it

It only filters when the fan runs. EPA says a furnace or central air filter works only while the system is running, usually less than a quarter of the time in the heating and cooling seasons. Running it longer filters more, but costs electricity and can make humidity harder to control in summer.

Change it on time. Lennox says inspect it monthly and replace it every one to three months, depending on the filter and the house: how often to change a furnace filter.

The right way round. The arrow on the frame points toward the furnace: which way a furnace filter goes.

Questions people ask

What does MERV stand for?

Minimum Efficiency Reporting Value. EPA says it reports how well a filter catches particles from 0.3 to 10 microns, from a test developed by ASHRAE.

Is MERV 13 too high for my furnace?

It can be. Trane says not every system can handle a MERV 13 because it can restrict airflow. Ask your heating and cooling company before switching.

MERV 8 or MERV 11?

Trane says MERV 8 may be enough with no pets or allergies, and MERV 11 is the better choice with pets because it also catches dander, skin flakes and hair.

Does a higher MERV filter use more energy?

If the system is not designed for it, yes. Lennox says a filter rated too high impedes airflow and increases energy use and wear.

Is a HEPA filter a MERV 16 or higher?

EPA says HEPA is not rated on the MERV scale. A HEPA filter catches 99.97 percent of particles at 0.3 micron, and HEPA is common in portable air cleaners.

Will a better filter help my allergies?

Possibly. EPA says studies with portable HEPA air cleaners found improvements in some allergy and asthma symptoms, but not always large ones.

Sources: EPA "What is a MERV rating?" and its Guide to Air Cleaners in the Home (2018), Trane "Filters by Number: MERV 8 vs MERV 11 vs MERV 13", Lennox "What is a MERV Rating?" and American Standard "What Is a MERV Rating?"