Furnace Filter Ratings, Explained Without the Marketing Fog
Every box shouts a different number: MERV 11, MPR 1000, FPR 7. They're three scales measuring roughly the same thing, and the higher one isn't always the one you want. Here's what the grades mean, side by side, and the rating most homes should actually buy.
table of contents
The furnace filter rating comparison chart
This is the table the filter aisle never puts in one place. Each row is roughly the same filter, labeled three different ways, plus what it captures and how often it typically needs changing:
| MERV (standard) | MPR (3M Filtrete) | FPR (Home Depot) | What it captures | Typical change interval |
|---|---|---|---|---|
| MERV 6 | MPR 300 | n/a | Dust, lint, carpet fibers | ~90 days |
| MERV 8 | MPR 600 | FPR 5 | Adds pollen, dust mites, mold spores | ~90 days |
| MERV 11 | MPR 1000–1200 | FPR 7 | Adds pet dander, fine dust, smoke residue | 60–90 days |
| MERV 12 | MPR 1500 | FPR 8–9 | Adds more sub-micron particles | ~60 days |
| MERV 13 | MPR 1900–2200 | FPR 10 | Adds smoke particles, bacteria, virus droplets | 60 days or less |
The equivalences are approximate because each system tests a little differently, but for buying decisions this is close enough. The one number every brand prints somewhere, even when it buries it, is MERV. That's the one to compare on.
MERV: the rating that actually matters
MERV stands for Minimum Efficiency Reporting Value. It's the only filter rating set by an independent standards body, ASHRAE, under test standard 52.2. The residential scale runs 1 to 16, and the number tells you how well the filter captures particles between 0.3 and 10 microns. Higher means it traps smaller particles.
Because it's a single industry standard, MERV is the only grade that lets you compare a Honeywell filter against a 3M filter against a store brand without doing mental math. Every other rating you'll see is a brand reframing of the same idea. If you remember one thing from this page: shop by MERV, ignore the rest.
MPR and FPR: the store-brand grades
MERV came first. Then marketing happened.
MPR (Microparticle Performance Rating) is 3M's own scale for its Filtrete line. It runs to 2800 and focuses on the smallest particles, the sizes where 3M's filters score well. A bigger-sounding number on a different scale feels more premium: MPR 1900 sounds far more impressive than its MERV 13 equivalent.
FPR (Filter Performance Rating) is Home Depot's color-coded 4-to-10 scale, used on brands it sells. It factors in things beyond raw particle capture, like how much weight the filter gains over its life, which is why FPR-to-MERV conversions sometimes disagree by a step between sources.
Neither scale is dishonest. They're designed so you can't stand in one store's aisle and directly compare that box against a competitor's box somewhere else. We break down the exact translations in our dedicated guide to MERV vs MPR vs FPR if you want the full conversion chart.
What's a good furnace filter rating?
For the large majority of homes, the answer lives between MERV 8 and MERV 11:
- MERV 8 is the baseline that protects your furnace and catches everyday dust, lint, and pollen. If nobody in the house has allergies and there are no pets, this is plenty.
- MERV 11 is the comfortable upgrade. It adds pet dander, fine dust, and smoke residue without much airflow penalty on most systems. This is the rating to default to if you have a pet or mild allergies.
- MERV 13 is the allergy, asthma, and wildfire-smoke tier. It captures bacteria and smoke particles, but it's denser and clogs faster, and not every furnace can pull air through it. Treat it as a deliberate choice, not an automatic upgrade.
If you want the full breakdown by household type, our guide to what MERV rating you actually need walks through pets, allergies, and system limits in detail.
Why higher isn't always better
This is the part the box won't tell you. A higher-rated filter is denser, and your blower has to pull air through that density. If your furnace wasn't designed for a high-MERV filter, forcing one in can:
- Reduce airflow, so rooms heat and cool unevenly.
- Raise energy use, because the blower works harder for the same result.
- Strain the system over time, especially older furnaces with a single 1-inch filter slot.
The genuinely best rating is the highest one your furnace manufacturer approves, not the highest number on the shelf. Check the manual or the panel inside the blower door before jumping to MERV 13. A MERV 11 filter that lets your system breathe beats a MERV 13 that strangles it.
kept stores the rating, size, and brand of the filter that fits your house, so the next purchase is a 10-second errand instead of another trip down the rating rabbit hole.
[ try kept free ]Which rating to buy by
Pick your rating once, then record three things so you never re-litigate it in the aisle:
- The MERV rating your system supports and your household needs, usually 8 to 11.
- The size, printed on the old filter's frame as width x height x depth, like 20x25x1. No filter in the slot? Here's how to find your furnace filter size.
- The change interval that matches your rating, from the chart above.
kept holds the size and brand of the filter that fits your house, so reordering takes seconds.
Those three facts turn every future filter run into a quick reorder on any brand's scale. Lose them, and you're back here in 90 days squinting at the boxes again.
Frequently asked questions
What is a good furnace filter rating?
For most homes, a MERV 8 to MERV 11 filter is the sweet spot. MERV 8 handles everyday dust, lint, and pollen. MERV 11 adds pet dander, fine dust, and smoke residue, which suits homes with pets or mild allergies. MERV 13 is the step up for allergies, asthma, or wildfire smoke, but only if your system can handle the denser filter without straining airflow.
What is the highest furnace filter rating?
The MERV scale runs from 1 to 16 for residential and light-commercial filters, with higher numbers capturing smaller particles. Ratings above MERV 16 exist (the HEPA range) but those are for hospitals and cleanrooms and will choke a typical home furnace. For a house, MERV 13 is effectively the practical ceiling, and even that requires a compatible system.
Is a higher MERV rating always better?
No. A denser filter captures more, but it also makes the blower work harder. If your furnace wasn't designed for a high-MERV filter, forcing one in can reduce airflow, raise energy use, and strain the system. The best rating is the highest one your manufacturer approves, not the highest number on the shelf.
What do furnace filter grades like MPR and FPR mean?
MERV is the industry-standard rating. MPR is 3M Filtrete's private scale (300 to 2800) and FPR is Home Depot's color-coded scale (4 to 10). Both track MERV loosely: MPR 1000 and FPR 7 are about MERV 11, while MPR 1900 and FPR 10 are about MERV 13. When comparing filters across stores, convert everything to MERV.
How often should I change a filter based on its rating?
Higher-rated filters trap more and clog faster, so the interval shortens as the rating climbs. A rough guide: MERV 8 about every 90 days, MERV 11 every 60 to 90 days, and MERV 13 every 60 days or sooner. Homes with pets, smokers, or heavy use should check on the shorter end of each range.