Using the right filter size and MERV rating keeps air flowing smoothly through your ductwork. Always match the measurements printed on your existing filter before selecting a replacement.
Parts with these numbers
16" x 25" x 4" MERV 8 Multi-Pleated Panel Filter (Hart & Cooley 102700026)
16" X 25" Media Air Filter (Honeywell Home FC100A1029)
- Length x width: match the size on the frame
- Depth: must match the slot: 1, 2, 4 or 5 in
- MERV: pick what your system can handle
Understanding 16x25x4 Filter Dimensions
The size printed on an air filter is its nominal size. Nominal measurements are rounded for easy identification. For example, a 16x25x1 filter really measures about 15.5 x 24.5 x 0.75 in. That is normal.
Your filter slot needs an exact physical match to seal properly. A 4-inch deep cabinet requires a 4-inch filter. Never try to force a thicker filter into a smaller slot.
- Nominal size: 16" x 25" x 4"
- Length and width: match the dimensions printed on the outer frame
- Depth: must match the filter slot depth of 1, 2, 4 or 5 in
Reading the Label and Arrow
Look at the cardboard frame on your old filter. The outer edge shows the length, width, and depth, along with the MERV rating. It also features a printed airflow arrow.
When sliding in the filter, point the airflow arrow toward the furnace or air handler, away from the return duct. Installing the filter backward can reduce efficiency and warp the media.
Comparing Available Options
Different models offer distinct MERV ratings and media materials. Choose the efficiency level that works with your specific HVAC system.
Many homes use MERV 8 to 11. A higher MERV rating catches more dust, but it can slow airflow on some systems.
- Hart & Cooley 102700026: nominal size 16" x 25" x 4", synthetic material, pleated panel filter type, MERV 8.
- Honeywell Home FC100A1029: nominal size 16" x 25" x 4", MERV 11, replaces CF100A1009.
Signs Your Filter Needs Attention
A dirty filter restricts the movement of air through your ductwork. Over time, heavy dust buildup makes your system work harder to push air into your living spaces.
Check a 1 in filter every month. Most need a change every 1 to 3 months. While a 4-inch media filter holds more debris than a thin panel, you should inspect it regularly for heavy gray dust accumulation.
How to confirm it fits
- Check that the frame reads 16" x 25" x 4". Match the length, width and depth printed on your old filter.
- Verify the depth fits the slot. A 4-inch slot requires a 4-inch filter, so never force an incorrect thickness.
- Check your system manual to ensure a MERV 8 or MERV 11 rating works for your system.
- Locate the airflow arrow on the frame and point it toward the furnace or air handler.
- If replacing part number CF100A1009, verify that model FC100A1029 matches your requirements.
Questions
Which direction should the airflow arrow point?
Point the arrow toward the furnace or air handler, away from the return duct.
What parts does Honeywell Home FC100A1029 replace?
Honeywell Home FC100A1029 replaces part number CF100A1009.
Can I use a higher MERV rating?
Many homes use MERV 8 to 11. Higher MERV catches more dust, but a higher MERV can slow airflow on some systems. Check your manual if you are unsure.
Why is my filter slightly smaller than 16x25x4?
The size on the label is rounded. Actual dimensions are slightly smaller than nominal dimensions so the frame fits easily into the slot.
Related guides
Brand names and part numbers are used only to show fit. HVAC Fitter is not affiliated with, authorized by, or endorsed by any equipment maker. If you are not sure a repair is safe for you, call a licensed HVAC technician.