Furnace Filters
The best furnace filter is the highest MERV rating your system can handle without restricting airflow, in the exact size printed on your current filter. EPA suggests MERV 13 or higher where your system allows, especially during wildfire smoke, while MERV 8 to 11 suits basic dust and allergy control.
How to choose
- Size: use the nominal size on the frame, such as 16x25x1 or 20x25x4. Actual dimensions are slightly smaller.
- MERV: higher numbers capture finer particles. MERV 13 captures a large share of fine smoke-size particles.
- System limits: check your HVAC manual. Some 1-inch systems struggle with dense filters.
- Thickness: 4- and 5-inch media filters have more surface area, lower resistance and longer life.
- Change intervals: 1-inch filters every 1 to 3 months, and 4-inch filters every 6 to 12 months.
- Filtrete uses its own MPR scale. Check the MERV equivalent on the package.
Shop MERV 13 Furnace Filters, MERV 11 Furnace Filters and Filtrete Furnace Filters.
FAQs
What MERV rating should I use?
Use the highest MERV your system handles well. MERV 8 suits basic dust protection, MERV 11 adds better capture of pet dander and fine dust, and MERV 13 is recommended by EPA for wildfire smoke and fine particles when the system allows. Check your HVAC manual or ask a technician.
How often should I change my furnace filter?
Typical guidance is every 1 to 3 months for 1-inch filters and every 6 to 12 months for 4- or 5-inch media filters. Change more often with pets, construction dust, smoke or heavy system use. A visibly gray, dust-caked filter is due regardless of the date.
Can a high-MERV filter damage my furnace?
A dense filter can restrict airflow in systems not designed for it, which may reduce efficiency or comfort and, in some cases, strain components. Many modern systems handle MERV 13, especially in 4-inch thickness. If airflow drops or rooms feel weaker, step down a rating or switch to a thicker filter.