Key Factors in Selecting the Right Air Filter Size and Fit

Choosing the correct air filter size ensures a tight seal in your HVAC return, preventing bypassed air and maximizing filtration efficiency while maintaining proper airflow and system performance.

Measure the length, width, and depth of the filter slot in inches, rounding to the nearest whole number to match standard nominal sizes.

Use a tape measure on the existing filter or the opening itself. Standard sizes include 16x20x1, 20x25x4, and many others. The actual dimensions may be slightly smaller; for example, a nominal 16x20x1 might measure 15.5x19.5x0.75 inches.

Write down all three dimensions in order: width, height, depth. This sequence matches how manufacturers label their products. Double-check your measurement before ordering to avoid returns and ensure a proper fit.

An undersized filter allows unfiltered air to bypass the media, while an oversized filter bows or buckles, reducing contact with the frame and letting contaminants through.

Gaps around the edges negate even the highest MERV rating. Dust flows through the path of least resistance. Over time, this bypass deposits debris on coils and fans, decreasing efficiency and increasing wear.

Forcing a too-large filter can damage the frame or block airflow entirely. A proper fit creates a seal that channels all return air through the media, delivering the filtration performance you expect.

Custom filters fill non-standard openings precisely, eliminating gaps and ensuring every cubic foot of air passes through the filtration media as designed.

Older homes and commercial buildings sometimes have unique dimensions. Off-the-shelf filters may leave small spaces around the perimeter. Custom fabrication matches your exact measurements, restoring full filtration coverage.

Suppliers like FiltXPO can produce filters to your specifications without long lead times. This service is especially valuable for facilities with multiple non-standard units, simplifying inventory and ensuring consistent quality.

One-inch filters fit most residential systems, while two- to five-inch filters offer greater media surface area, higher MERV capacity, and longer service life in commercial or high-demand settings.

Deeper filters accommodate more pleats, which increases particle-holding capacity and reduces pressure drop. A four-inch MERV 13 often lasts six months, compared to 90 days for a one-inch MERV 11.

Check your system's filter cabinet depth before upgrading. Some units have adjustable tracks or expandable housings. If yours does not, you must stay within the original depth to maintain proper fit and airflow.

Accurate sizing is the foundation of effective air filtration. Taking time to measure and order correctly pays off in cleaner air and smoother HVAC operation.

FiltXPO offers standard and custom air filter sizes for any application. Start your order today by calling 919-459-3700 and receive filters that fit your system perfectly every time.