Pick MERV 13 when your system can accept it, since the U.S. Environmental Protection Agency (EPA) rates it above MERV 11 in every particle band it lists. At The Indoor Report, we explain what each published MERV figure means for a home decision.
MERV reports a filter's ability to capture particles between 0.3 and 10 micrometers (µm). EPA says the rating is particularly helpful for comparing filters for furnace or central heating, ventilation, and air conditioning (HVAC) systems. Box labels such as an 'allergen' or 'performance' scale are not the MERV scale, so read the MERV number stated on the package.
The number alone does not settle the purchase. A system's fan and filter slot decide how high a rating it can take, and EPA ties any upgrade to that limit.
EPA's Table Rates MERV 13 Above MERV 11 in Every Particle Band
MERV 13 captures a larger minimum share of every particle band that EPA's table lists than MERV 11 does. The EPA MERV page gives minimum capture percentages for MERV 11 and MERV 13 across three size bands.
EPA says the higher the MERV rating, the better the filter is at trapping specific sizes of particles. The one-line rule from EPA for upgrading is to choose at least MERV 13, or as high a rating as your system fan and filter slot can accommodate.
Every figure in the table is a minimum. Read 'at least 50%' as the floor the MERV 13 rating sets for that band.
MERV 11 Captures at Least 20% of the Smallest Listed Particles
EPA's table gives MERV 11 three minimum figures: at least 20% for particles from 0.30 to 1.0 µm, at least 65% for 1.0 to 3.0 µm, and at least 85% for 3.0 to 10.0 µm.
The 20% figure in the smallest band is the lowest of MERV 11's three numbers, and it is the figure to set against MERV 13's 50% in that same band. The largest band carries MERV 11's highest figure, at 85%.
EPA's table lists MERV 8 with no figure for the 0.30 to 1.0 µm band, so MERV 11 is the first rating in the table that states one.
MERV 13 Widens the Gap Most in the 0.30 to 1.0 Micron Band
EPA's table gives MERV 13 at least 50% for particles from 0.30 to 1.0 µm, at least 85% for 1.0 to 3.0 µm, and at least 90% for 3.0 to 10.0 µm.
Set against MERV 11, the gap is 30 percentage points in the smallest band (50 minus 20). The middle band gap is 20 points (85 minus 65), and the largest band gap is 5 points (90 minus 85).
The smallest band is where the two ratings differ most, so that is where MERV 13 pulls furthest ahead. The largest band shows the closest pair of figures, at 85% and 90%.
HEPA (high-efficiency particulate air) filters use a different rating system. EPA says HEPA filters capture at least 99.97% of 0.30 µm particles and that its HEPA figures are not based on the MERV scale. For a unit built around that standard, see HEPA air purifiers.
The MERV Number Leaves Out Fan Limits, Replacement, and Run Time
It does not decide whether a given system can use the filter, and that question depends on the fan and filter slot.
The EPA guide to air cleaners in the home says furnace and HVAC filters filter the air only while the system is operating. In most cases, HVAC systems run only when heating or cooling is needed, usually less than 25% of the time during heating and cooling seasons. EPA says longer run times increase electricity costs and may result in less reliable humidity control during the cooling season.
EPA says central furnace or HVAC filters are designed to filter air throughout a home. EPA also says filtration supplements source control and ventilation, and that filters cannot remove all pollutants. The EPA page on air cleaners and air filters states both points.
EPA says all filters need periodic replacement to work properly, so follow the manufacturer's recommendations on maintenance and replacement.
Fan and Filter Slot Limits Decide Whether MERV 13 Fits Your System
EPA says you may need a professional HVAC technician to determine the highest efficiency filter that works for your system (per EPA's MERV page).
The depth, the fan, and the slot each limit which MERV rating a system takes. Pressure-drop and airflow figures are not published here, so a technician should check them for your system.
Filter size is a separate decision from MERV. Check the length, width, and depth against HVAC filter sizes before you compare ratings.
For the MERV 13 product side of the decision, see MERV 13 filters.
MERV 11 and MERV 13 Specifications Side by Side
The table places each EPA figure beside its rating, and every cell names its source.
| Dimension | MERV 11 | MERV 13 |
|---|---|---|
| 0.30 to 1.0 µm capture | At least 20%, per EPA's MERV table | At least 50%, per EPA's MERV table |
| 1.0 to 3.0 µm capture | At least 65%, per EPA's MERV table | At least 85%, per EPA's MERV table |
| 3.0 to 10.0 µm capture | At least 85%, per EPA's MERV table | At least 90%, per EPA's MERV table |
| Test method and source | ASHRAE test method, per EPA | ASHRAE test method, per EPA |
| Fit consideration | EPA's upgrade advice does not name MERV 11; it names MERV 13 or the highest rating the system accepts | EPA's upgrade advice names MERV 13, or as high a rating as the fan and filter slot accommodate |
Which MERV Rating to Choose for Your System
The answer depends on what your system accepts. If the fan and filter slot take MERV 13, EPA's upgrade advice points to MERV 13, and EPA's table gives it the higher minimum in every band. If they do not take MERV 13, EPA says to use the highest rating the system accommodates, and EPA names no specific fallback MERV number.
A system whose fan or filter slot cannot take MERV 13 is not a fit for this pick. This comparison also does not serve readers choosing by a named pollutant, because EPA's table lists particle sizes and names no pollutants. For a standalone unit, start with HEPA air purifiers.
The verdict would change if a technician finds that your fan or filter slot cannot accept MERV 13, because the highest accepted rating would then govern the choice.
For the MERV 11 vs MERV 13 choice, the next step is to read the stated MERV number on the package you are considering, then confirm with a technician whether your fan and filter slot accept MERV 13, as EPA's MERV page suggests.
Common questions
Is MERV 13 better than MERV 11?
On the minimum figures EPA publishes, yes. MERV 13 is at least 50%, 85%, and 90% across the three bands, and MERV 11 is at least 20%, 65%, and 85%, per EPA's MERV table. Whether MERV 13 is the right pick depends on whether your fan and filter slot accept it, and EPA says a professional HVAC technician may be needed to decide (per EPA's MERV page).
What drives the cost of MERV 11 versus MERV 13 filters?
EPA says all filters need periodic replacement and that longer HVAC run times increase electricity costs. Compare each product's replacement recommendations.
Does a MERV 13 filter catch pet dander and smoke?
EPA's table lists capture by particle size and names no pollutants, so it gives no figure for pet dander or smoke. The table's smallest band covers 0.30 to 1.0 µm particles, but the table does not map that band to any named pollutant. EPA says filters cannot remove all pollutants and that filtration supplements source control and ventilation. For a standalone approach, see air purifier vs air filter.
Is a higher MERV rating always better?
No. EPA says the higher the rating, the better a filter traps specific particle sizes, but its upgrade advice ties the choice to as high a rating as your fan and filter slot can accommodate. EPA says a professional HVAC technician may be needed to find the highest efficiency filter that works (per EPA's MERV page).
MERV 13 vs MERV 11: which does EPA's table favor?
EPA's table does not rank MERV 11 above MERV 13 in any particle band. If a system cannot accept MERV 13, EPA does not name MERV 11 as the fallback. EPA says to use the highest rating the fan and filter slot accommodate, so the right rating depends on what your system accepts.
How often should a MERV 13 filter be replaced?
EPA says all filters require periodic replacement to function properly, and it tells readers to follow the manufacturer's recommendations on maintenance and replacement. The interval is set by the manufacturer, not by EPA's table, so the schedule that applies comes from the manufacturer's own maintenance guidance.