Rating Systems Explained

If you’ve been shopping for filters, you may have noticed that not all filters are rated by the same rating system. It can be confusing trying to understand how each system stacks up, and how to determine which filter you switch to a differently rated filter.

We’ll try to help you make sense of these differences and make you aware of all the systems currently being used. If you happen to be reading this in the store now, jump down to the graphic below for a quick comparison at a glance.

What systems are there?

Currently, there are four filter rating systems currently in use in North America for rating the filtration ability of home filters.

MERV/ ASHRAE 52.2: Introduced in 1987, this has been a standard the standard for filter rating for a long time. Many products in the North American market still display this rating, but the entire market is already shifting away from MERV as manufacturers are having their filters retested against the new ISO 16890 standards. The MERV scale goes from 1 – 20, but you will often only find MERV 1 – 13 for home HVACs. Read more about MERV Ratings here https://www.nafahq.org/understanding-merv/


ISO 16890: The new global ISO standard was introduced in 2017 to replace the MERV/ASHRAE rating system. This rating system was created to address some of the shortcomings of the MERV system. The new 16890 system does a far better job of accounting for real-world scenarios and places more focus on smaller particles of 3 microns or less. This better aligns testing conditions with the particle sizes found commonly in homes and is a much more accurate rating of the performance homeowners will see. This scale looks at the percentage of particulate removed at various particulate sizes and provides a final classification by combining these scores. Filter ratings will be displayed as a percentage of particulate removed from the air for each particle size group. For an in-depth dive, check out this video [https://www.youtube.com/watch?v=8jCQ7T4UgmY] from Mann+Hummel.


FPR (Filter Performance Rating): A rating system unique to The Home Depot. This system is used on all brands sold through their retail store. Their rating system is color coded and closely numbers relatively align with the MERV rating system.


MPR (Micro-Particle Performance): A rating system created by 3M. This rating system only exists on 3M products and exclusively rates the filter’s ability to capture airborne particles smaller than 1 micron.

The Comparison

This chart should help you to try and understand how filter ratings stack up in within each system. Please note that each system determines their values with their own testing procedures. Not all testing is performed in the same way across each rating system. There will be some subjective discrepancies, but this chart should provide close estimates for comparison.

Breezi helps explain the MERV rating system
Breezi helps explain the MERV rating system