Furnace filter guide
MERV vs MPR vs FPR: The Only Furnace-Filter Rating That Means Anything
Three ratings sit on furnace-filter boxes, but only one is a real standard. MERV is defined by ANSI/ASHRAE 52.2. MPR and FPR are private marketing scales owned by 3M and Home Depot. Here is how they map, and why we score the MERV.
Only MERV is a real standard
MERV (Minimum Efficiency Reporting Value) is defined by ANSI/ASHRAE Standard 52.2, an independent industry standard that tests how well a filter captures particles across a range of sizes. It runs 1 to 16 for residential filters, and every brand can be measured against the same yardstick. That is what makes it useful: a MERV 13 from one brand means the same thing as a MERV 13 from another.
MPR and FPR are not standards. MPR (Microparticle Performance Rating) is a scale 3M created and controls for its Filtrete line. FPR (Filter Performance Rating) is a scale used by Home Depot for the filters it sells. Each company defines its own scale, so the numbers are not comparable across brands and are not independently verified.
How the proprietary numbers map to MERV
The marketing scales run on bigger, more impressive-looking numbers. 3M's MPR goes into the thousands; Home Depot's FPR runs 4 to 10. Here is the practical conversion for the most common products: MPR 1500 is about MERV 12, and MPR 1900 is about MERV 13. FPR 10 is roughly MERV 13 in a 1-inch filter.
The trap is that the same proprietary number can map to different real MERV depending on the filter. Home Depot's FPR 10 is MERV 13 in the 1-inch panel but only MERV 12 in the 4-inch media. A scale where the same number means two different things is not a scale you can shop on. Convert to MERV, then compare.
Why we score the MERV, not the marketing number
FilterScored credits the true ANSI/ASHRAE 52.2 MERV and rewards brands that print it plainly. A filter that hides its MERV behind an MPR or FPR number is marked down on rating honesty, because the buyer cannot compare it against anything. This is the same principle as our water rule that a marketing claim is not a third-party certification.
None of this means a Filtrete or Home Depot filter is bad. A Filtrete MPR 1900 is a genuine MERV 13 filter. The markdown is for obscuring the standardized number, not for the filtration itself. A brand that printed MERV 13 plainly would score higher on the same physical product.
The depth tradeoff nobody mentions
A high MERV rating in a thin 1-inch filter has a hidden cost: airflow restriction. A 1-inch MERV 13 filter packs fine media into a small surface area, which can restrict airflow enough to strain the blower on some systems, especially older ones. The same MERV 13 in a 4-inch or 5-inch deep-media filter has far more surface area and restricts airflow much less.
So the technically right way to run MERV 13 is in deep media, not a 1-inch panel. If you only have a 1-inch slot, a MERV 11 often balances filtration and airflow better than a MERV 13. We flag high-MERV 1-inch filters for this on their scorecards.
FAQ
- Is MPR 1900 the same as MERV 13?
- Roughly, yes. 3M's MPR 1900 corresponds to about MERV 13 on the standardized ANSI/ASHRAE 52.2 scale, and MPR 1500 to about MERV 12. MPR is 3M's own scale, so always convert to MERV to compare across brands.
- Is a higher MERV always better?
- Not in a 1-inch filter. A high-MERV 1-inch filter can restrict airflow and strain the blower. High MERV belongs in deep 4-inch or 5-inch media; in a 1-inch slot, MERV 11 is often the better balance. Check your system's tolerance.
- Why do brands use MPR and FPR instead of MERV?
- Bigger numbers market better, and a proprietary scale is not directly comparable to competitors. MERV tops out at 16 for homes; MPR runs into the thousands, which looks more impressive on a shelf. We score the MERV so the comparison is honest.
Sources
Browse air purifier scores or water filter scores.