đŦī¸ Air Filter Size Finder
Find the right air filter size and MERV rating for your HVAC system. Includes replacement schedules and MERV rating explanations.
How to Use This Calculator
Select your filter size from the common sizes dropdown, or enter custom dimensions manually. Then select your desired MERV rating. The tool shows your exact filter size, recommended replacement schedule, and whether the MERV rating is compatible with your filter depth.
Understanding Your Results
Nominal filter size is what you'll see on the packaging. Actual size is slightly smaller (usually by about 3/8" to 1/2"). Higher MERV ratings capture smaller particles but can restrict airflow â this is especially important with 1-inch filters. If you want better filtration, consider upgrading to a 4-inch filter cabinet, which allows higher MERV ratings without airflow restriction.
Frequently Asked Questions
How do I find my air filter size?
Check the existing filter for printed dimensions. Filter sizes are listed as length x width x depth (e.g., 20x25x1). If no filter is installed, measure the filter slot opening.
What MERV rating should I use?
MERV 8-11 is good for most homes (captures dust, pollen, mold). MERV 13+ captures finer particles including some bacteria and smoke. Higher MERV ratings restrict more airflow, so check your system's compatibility.
How often should I change my air filter?
Standard 1-inch filters: every 1-3 months. 4-inch filters: every 6-12 months. Homes with pets, allergies, or high dust should change more frequently.
Do MERV ratings affect energy costs?
Higher MERV filters create more airflow resistance, which can increase energy use slightly. However, a clean MERV 13 filter causes less restriction than a dirty MERV 8 filter. Regular replacement is key.