Measuring Length and Width (L x W). (If your filter is not a square, the smallest measurement goes first).
Measure the thickness (Depth) of your filter from front to back.
Put Your measurements together (L x W x D).
A filter’s true dimensions.
Example: 19.75” x 19.75” x 1”
Rounded numbers used by manufacturers.
Example 20” x 20” x 1”
View Detailed InstructionsAprilaire 210 Replacement Air Filter
MERV ratings let you know the efficiency and level of filtration that an air filter can handle under normal circumstances. The higher the MERV rating, the finer the particles are that are filtered our of the air in your home. Many air filter retailers use MERV or a similar rating to rate their air filters.
MERV Rating is the primary rating system used in the industry, both domestically and internationally. Established by the American Society of Heating, Refrigerating, and Air Conditioning Engineers, MERV rates a filter’s ability to capture and hold particles and pollutants.
MPR Rating is a rating system developed by 3M. It rates the manufacturer’s Filtrete product line and their ability to capture airborne particles smaller than 1 micron.
FPR Rating is a rating system developed by The Home Depot for brands sold through their stores, including Honeywell. It utilizes a color code and number scale (4 to 10) that closely resembles the MERV rating.
