Best filter if you only want to change it quarterly
If you want to replace your furnace filter only four times a year, choose a correctly sized pleated filter with a MERV rating your HVAC…
Setup & accessories
Help choosing furnace filter size and MERV rating without starving the furnace for air.
Maintenance
Pleated 1 inch in a 3-month change cadence
A 1-inch pleated filter can often be changed every three months, but dust, pets, smoke, construction, and airflow restrictions may require…
How often to change a furnace filter
Most 1-inch furnace filters need changing about every 1 to 3 months, but the right schedule depends on filter thickness, airflow, pets,…
Filter reminder magnet versus a calendar
A reminder magnet is easier to notice near the furnace; a calendar is better for recurring alerts and shared schedules. Either works if you…
Professional Duct Cleaning Versus Just Changing Filters
A clean filter helps trap new airborne particles and protect HVAC airflow, but it does not remove debris already inside ductwork. Most…
When to Replace a Furnace Filter After Renovation Dust
After a dusty renovation, inspect your furnace filter and replace it if it is visibly loaded, damaged, or restricting airflow. Check it…
Writing the install date on the frame
Write the installation date on an exposed edge of the filter frame, not on the filter material. Keep the airflow arrow and size label…
Setup
Buying after matching the arrow and the rack
Once the airflow arrow and filter rack point you to the correct installation, confirm the actual filter dimensions and choose a MERV rating…
How to Change a Furnace Filter
Changing a furnace filter is usually a quick, tool-free task. Find the filter, confirm its size, install it with the airflow arrow pointing…
Two 1 inch filters stacked is usually wrong
Stacking two 1-inch furnace filters usually does not equal one thicker filter. It can restrict airflow, increase furnace strain, and make…
Finding the Filter Slot on a Basement Furnace
A basement furnace filter is usually in the return-air duct near the furnace, behind a return grille, or inside an accessible furnace…
Which Way the Airflow Arrow on a Furnace Filter Faces
The arrow on a furnace filter points the way air travels through it. Follow the airflow toward the HVAC equipment—or into the return duct…
Sizing
1 inch versus 4 inch versus 5 inch filters
The right furnace filter thickness depends on your HVAC cabinet, airflow needs, and the filter’s actual MERV rating—not thickness alone.…
Actual 19.5 x 24.5 versus a 20x25 nominal
A filter marked 20x25 may have actual dimensions near 19.5x24.5 because furnace filter sizes are commonly nominal. Measure the old filter,…
Family of sizes: 16x20, 16x25, 20x25
The right furnace filter is the one that fits the filter slot, matches the required thickness, and provides suitable filtration without…
How to Measure an Existing Filter With No Printed Size
Measure the filter’s length, width, and thickness, then compare those actual dimensions with the nominal size used on filter packaging.…
How to Read Furnace Filter Size | Actual vs. Nominal Dimensions
Furnace filter sizes are usually printed as nominal dimensions, which may be slightly larger than the filter’s actual measurements. Here’s…
Nominal versus actual filter dimensions
Furnace filter sizes are usually labeled with rounded nominal dimensions, while the filter itself is slightly smaller. Learn how to measure…
