Home › 16x25x4
16x25x4
Quick answer: A 16x25x4 is a deep media filter with the same face as a 16x25x1 but several times the pleated media. Actual size is about 15½ × 24½ inches, with depth often around 3⅝ to 3¾ inches, though some cabinets need a different depth. It fits a media cabinet at the furnace and is often changed every six to twelve months.
What makes a 4-inch filter different
The face of a 16x25x4 is the same as its 1-inch cousin, but the deep frame holds tall, tightly folded pleats. That gives the air far more surface to pass through. The practical results are lower airflow resistance at the same MERV rating, slower loading and much longer intervals between changes. That is why media cabinets are a common way to run MERV 11 or MERV 13 without straining a residential blower.
Dimensions and the depth problem
| Measure | Nominal | Typical actual |
|---|---|---|
| Width | 16 in | about 15½–15⅝ in |
| Length | 25 in | about 24½–24⅝ in |
| Depth | 4 in | often about 3⅝–3¾ in; some cabinets differ |
| Face area | 2.78 ft² | about 2.64 ft² actual |
Depth is the tricky part. Different media cabinet makers designed their housings around different depths. Some take a filter around 3⅝ inches; others are labelled 4 inches but need about 4⅜ inches; still others are called "5-inch" and take around 4⅞. Always check the cabinet label or manual, or measure the old filter's frame depth, before buying.
Is your cabinet 4-inch or 5-inch?
Look at the cabinet door for a brand and model number. Measure the inside depth of the filter channel. Compare with the old filter's printed actual size. If the old filter's packaging named a specific cabinet model, buy replacements listed as compatible with that model.
Airflow advantage
At 1,000 CFM, the face velocity on a 16x25 is about 360 fpm whatever the depth. But because a 4-inch filter spreads that air over much more media, the velocity through the media itself is much lower, so resistance is lower too. A 4-inch MERV 13 often shows initial resistance similar to or lower than a 1-inch MERV 8. Check the specific product's data sheet for numbers; see airflow and pressure drop.
Worked example
A homeowner with a 16x25x4 cabinet on a 2.5-ton system (about 1,000 CFM) is replacing a MERV 8 media filter with MERV 13. The cabinet label specifies an actual depth of 3⅝ inches. They buy a compatible filter at a hypothetical $42, planning to inspect at six months and replace by nine. Annual cost is about $56. Compared with a 1-inch MERV 13 at a hypothetical $20 changed every 60 days — about $122 a year — the deep filter costs less and is easier on the blower.
Illustrative note (2026-10-29): This example was prepared on 2026-10-29 for illustration. Prices, depths and intervals are hypothetical; follow your cabinet maker's and filter maker's specifications.
Expandable vs cartridge media
Some media cabinets use an expandable pleat pack: a folded block of media that you stretch into a reusable metal or plastic frame. Others use a one-piece cartridge with its own cardboard frame. Replacement filters must match your cabinet's style. Cartridges are simpler; pleat packs can be cheaper but take a minute to install correctly.
Change interval
Six to twelve months is a common guideline for deep media filters. Homes with pets, heavy dust, smoking or construction may need replacement sooner. A filter that is visibly grey and caked, or that bows, needs changing regardless of the date. The schedule tool suggests a starting range.
Sealing the cabinet
Media cabinets rely on door gaskets and filter edge seals. Check that the door closes snugly and that the gasket is not torn. Dust streaks around the door indicate leakage. Replacement gaskets are usually available from the cabinet maker.
Upgrading to a media cabinet
If you currently use a 1-inch filter, an HVAC contractor can install a cabinet on the return side of the furnace, subject to space and duct layout. The work involves cutting into the return plenum and sealing the new cabinet, so it is a professional job.
Changing it
- Switch the system off at the thermostat.
- Open the cabinet door and slide the old filter out, noting the arrow.
- Vacuum dust from the cabinet channel.
- Slide the new filter in with the arrow toward the furnace.
- Close the door and check the latches.
Common cabinet families
Several well-known furnace and filtration brands sell media cabinets in 16x25 and 20x25 face sizes. Over decades, some redesigned their cabinets, so two cabinets from the same brand may take different depths. Generic replacement filters are usually listed by the cabinet model they fit, sometimes with the actual dimensions in the title. When the listing shows several depth options for the same face size, pick the one matching the actual depth printed on your old filter, not the nominal "4-inch" label.
Buying replacements
Because media filters are changed rarely, it is easy to forget what you bought last time. Keep the old filter's label, or photograph it, before throwing it out. Note the brand, the actual dimensions, the MERV and the cabinet model. Some households buy two at once so a spare is ready when the time comes. Media filters ship in larger boxes, so local availability can be patchier than for 1-inch sizes; ordering ahead avoids running the system without a filter.
Running without a filter
Never run a furnace with an empty media cabinet while you wait for a replacement. Unfiltered air carries dust straight onto the blower wheel and cooling coil, which can reduce efficiency and require professional cleaning. If you must wait, a temporary 1-inch filter is not a good seal in a deep cabinet; it is better to keep a spare on hand.
Frequently asked questions
Can I use a 16x25x4 in a 16x25x1 slot?
No. It will not fit. You need a media cabinet.
Are all 16x25x4 filters the same depth?
No. Depth varies by cabinet design; match your cabinet.
Does a 4-inch filter need changing less often?
Usually yes, often six to twelve months, but inspect it.