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16x20x1
Quick answer: A 16x20x1 filter measures about 15½ × 19½ × ¾ inches in reality. It is common in smaller furnaces, wall and ceiling return grilles, and apartments. Its nominal face area is about 2.22 square feet, so at a typical 300 fpm it handles around 670 CFM — enough for a system of up to roughly 1.5–2 tons.
A smaller workhorse
The 16x20x1 is the shorter sibling of 16x25x1. It turns up where space is tight: compact furnaces in closets, return grilles in apartments and condos, and homes with multiple smaller returns rather than one big one. Because so many homes use it, it is one of the easiest sizes to find on the shelf, in fibreglass and pleated versions from MERV 4 to MERV 13.
Dimensions
| Measure | Nominal | Typical actual |
|---|---|---|
| Width | 16 in | about 15½ in |
| Length | 20 in | about 19½ in |
| Depth | 1 in | about ¾ in |
| Face area | 2.22 ft² | about 2.10 ft² actual |
Common locations
- Hallway return grilles in apartments and condos.
- Closet furnaces and small air handlers.
- Multiple return grilles in larger homes, each with its own 16x20x1.
- Some packaged terminal and through-wall systems — check the manual, because many use proprietary filters.
Airflow math
At 300 fpm, a 16x20 filter passes about 2.22 × 300 ≈ 667 CFM. A 1.5-ton system moving around 600 CFM lands at about 270 fpm, a comfortable velocity. A 2.5-ton system moving 1,000 CFM through one 16x20x1 would hit about 450 fpm, which pushes resistance up sharply. In those homes, there are usually two or more returns, each sharing the load. If you have one small grille and a big system, ask an HVAC technician whether the return is undersized.
Picking efficiency
For small systems with short duct runs, MERV 8 or MERV 11 in 16x20x1 is a sensible range. MERV 13 is available but adds resistance, and small returns have less margin. Watch for whistling at the grille after any upgrade; with a 16x20, noise is often the first sign of too much restriction.
Worked example
An apartment has a 1.5-ton air handler in a closet and one 16x20x1 ceiling return. Airflow is roughly 600 CFM, so face velocity is about 270 fpm. The tenant has been buying basic fibreglass filters. They switch to MERV 8 pleated at a hypothetical $8 each, changed every 60 days, costing about $49 a year. Before making the change, they check the lease: the landlord supplies filters, so the tenant asks whether they can use pleated ones instead.
Illustrative note (2026-10-29): This example was written on 2026-10-29 for illustration. The apartment, airflow, price and lease terms are hypothetical.
Multiple 16x20 returns
Larger homes sometimes have two or three 16x20x1 grilles instead of one large filter. Each needs changing on the same schedule; it is easy to forget the one in the upstairs hallway. Label each grille's size inside its door and change them together. If there is also a filter at the furnace, ask a technician whether both are intended — doubling up adds resistance.
Similar sizes to watch
- 16x20x1 vs 14x20x1: two inches narrower — leaves a big gap.
- 16x20x1 vs 16x21x1: a less common size used by some furnaces.
- 16x20x1 vs 16x20x4: same face, but only the 4-inch fits a media cabinet.
Measure if in doubt with how to measure.
Installation
Point the arrow into the grille (toward the duct) or toward the air handler. Close grille latches fully. If the grille door has warped and no longer seals, a technician or building maintenance can replace it; gaps around it let air bypass the filter.
Change interval
A 16x20x1 handles less air area than larger filters, so in a busy home it loads relatively quickly. One to three months is common; check it monthly the first season. Use the schedule tool for a starting point.
Cost
Smaller filters are usually a bit cheaper than 16x25 or 20x25 at the same MERV. Multi-packs help. Run your numbers in cost per year.
Renters
In many rentals, filter changes are the landlord's responsibility, or the lease may assign them to tenants. Check your lease and ask building management. See apartment filters.
Fibreglass versus pleated in this size
Flat fibreglass 16x20x1 panels are the cheapest option and are often what building maintenance stocks by the case. They mostly stop large debris from reaching the blower and coil and let air through easily. Pleated 16x20x1 filters cost more but fold extra media into the frame, capturing far more fine dust at a usually modest resistance increase. For a small system with a short return, pleated MERV 8 is a common middle path. Whichever you use, the key is changing it before it clogs, because a small filter clogs sooner than a large one.
Checking a ceiling grille safely
Ceiling returns mean working overhead. Use a stable step stool, open the grille slowly because dust may fall, and hold the filter flat as you lower it. Wear a dust mask if you are sensitive to dust, and have the new filter ready so the grille is open only briefly. If the latches are stiff or broken, report them to building maintenance rather than forcing them.
Keeping track
With a size this common, it helps to buy a multi-pack and write the change date on each frame when installed.
When the size seems wrong
If a 16x20x1 slides in loosely or the grille will not close, re-measure the frame. Some older buildings use 16x21 or 15x20 grilles that look nearly identical from the room, and a quick tape check settles it in seconds.
Quick reference
Nominal 16x20x1, actual about 15½ × 19½ × ¾ inches, arrow toward the equipment, check monthly.
Frequently asked questions
Will a 16x20x1 fit a 16x25 slot?
No. It is five inches short and leaves a large gap. Buy the matching size.
Is MERV 13 OK in a 16x20x1?
Possibly, but small returns have less margin. Confirm airflow with a technician first.
My filter says 15.5x19.5. What do I buy?
A 16x20x1.