Actual Size: 15.5x19.5x3.63
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Available In MERV Rating: 8, 11, 13
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 MERV 8 |  MERV 11 |  MERV 13 | |
|---|---|---|---|
| Best for | Standard Residential/Commercial Healthy Families | Superior Residential/Commercial Allergy Sufferers | Optimal Residential/Commercial Hospital Grade |
| Comparable ratings | MPR 600 & FPR 5 | MPR 1000-1200 & FPR 7 | MPR 1500 - 1900 & FPR 10 |
| Filtration | Captures 90% of Airborne Particles | Captures 95% of Airborne Particles | Captures 98% of Airborne Particles |
| Dust, lint & debris | |||
| Mold, pollen | |||
| Dander, dust mites | |||
| Smoke & Smog | |||
| Bacteria | |||
| Odor, vocs |
Generally, we recommend you replace your air filters every 90 days. Find out below if you should change your filters more often.
Change your filter every
6 weeks
to ensure indoor air quality is at its best.
Change your filter every
2 months
to avoid shedding and odor buildup.
Change your filter every
2-3 months
as having clean air is even more important with children in your home.
Change your filter every
6 weeks
to ensure indoor air quality is at its best.
Change your filter every
2 months
to avoid shedding and odor buildup.
Change your filter every
2-3 months
as having clean air is even more important with children in your home.
Actual size: 15.50" × 19.50" × 3.63"
Author: Michelle Wan, Brand Manager & Air Quality Writer | Reviewer: David Clark, Licensed HVAC Technician |
Updated: August 14, 2026
A 16x20x4 air filter is a four-inch-deep pleated filter for central furnace and air conditioning systems, and the actual cut measures 15.50" × 19.50" × 3.63". Filterbuy cuts, pleats, and frames it to order in our own US plants, in MERV 8, MERV 11, and MERV 13. MERV 8 is the standard choice for most homes. Check your HVAC manual to confirm which rating your system takes.
MERV 8 is the standard choice for most homes. Step up to MERV 11 for pets and pollen, or MERV 13 for smoke.
A Filterbuy 16x20x4 lasts 6 to 9 months. The 90-day rule you've heard applies to one-inch filters.
The actual cut is 15.50" × 19.50" × 3.63". "16x20x4" is the ordering name, and the clearance is what makes the filter fit.
Check your HVAC manual before you choose a rating. It's a normal fit check, the same as confirming a size.
A Filterbuy 16x20x4 air filter measures 15.50" × 19.50" × 3.63". We cut, pleat, and frame every one to order in our own US plants, so that is the cut spec rather than an estimate. "16x20x4" is the ordering name. The filter is cut smaller by design, and that clearance is what lets it slide into the slot. Brands don't all leave the same clearance, so a same-size filter from elsewhere won't always sit the way yours does.
To confirm your size, measure the old filter first. Take length, width, and depth, then round up to the nearest inch. Almost everyone finds their size in our list. If yours isn't there, we cut custom sizes to the eighth of an inch.
MERV 8 is the standard choice for most homes. MERV, short for Minimum Efficiency Reporting Value, is the industry scale for how much a filter captures. We make 16x20x4 in three ratings, and the right one depends on what you're dealing with at home.
Check your HVAC manual to confirm which MERV rating your system takes, the same way you would confirm a size.
MERV 8 is the standard choice for most homes. Shop Filterbuy 16x20x4 MERV 8 filters.
MERV 11 is built for allergy sufferers, and it's the one to pick if you have pets or pollen coming in. Shop Filterbuy 16x20x4 MERV 11 filters.
MERV 13 is our optimal tier, and it's the one for smoke. Shop Filterbuy 16x20x4 MERV 13 filters.
Odors are a different job. Cooking smells and pet odors call for our Odor Eliminator carbon filter rather than a higher MERV number.
Whichever rating you pick, check your HVAC manual to confirm what your system takes. It's a normal fit check, the same as confirming a size. For health questions about your air, talk to a qualified professional.
A Filterbuy 16x20x4 air filter lasts 6 to 9 months, not 90 days. That 90-day rule was written for one-inch filters. Four inches of media loads far more slowly, still working long after a thin filter would choke.
Ranges reflect Filterbuy's published service life for 4-inch filters. The EPA advises replacing per the manufacturer's recommendation, and sooner if a filter looks soiled.
The surest check is your own eyes. Hold the filter up to a light. If no light comes through the pleats, swap it whatever the calendar says.
Don't want to think about it again? Set up auto-delivery and save 5%.
A 16x20x4 filter fits central forced-air systems with a four-inch cabinet, and one filter serves both heating and cooling. Your furnace and air conditioner share one air handler and one filter slot, so there is no separate "furnace filter" to buy. What varies between brands is the cabinet's internal dimensions.
A four-inch filter only fits a media cabinet, the boxed housing on the return side of your furnace with a hinged door or slide-out slot. If your filter drops into a wall grille or a thin track at the furnace base, you've got a one-inch system. Buying a thicker filter won't upgrade a one-inch slot. That takes a new cabinet and a technician, and we'd rather tell you now than ship you a Filterbuy filter that can't go in.
Check the seal before you trust the rating. Look for daylight or slack at the edges. In a cabinet built for a 4.31-inch filter, ours sits about two-thirds of an inch shallow, so the rails have to hold it square. A MERV 13 filter that isn't sealing does less for you than a MERV 8 that is. The EPA's Guide to Air Cleaners in the Home says it plainly: the filter has to fit snugly so air doesn't leak around it.
The MERV rating is printed on the long edge of the filter's cardboard frame, alongside the size and airflow arrow. Slide it partway out and read the side facing you. If the number isn't labeled MERV, that brand is using its own scale. 3M and Filtrete use MPR; Home Depot uses FPR. Per the EPA, MERV is a national consensus standard while MPR and FPR are proprietary, so equivalents are approximate.
MPR and FPR are third-party rating systems owned by their respective companies, not Filterbuy scales, so equivalents are approximate.
If the frame shows no rating, it's almost certainly a fiberglass panel, typically MERV 1–4, which protects the equipment rather than the air. See our guide to MERV ratings.
A 16x20x4 is one of the hardest sizes to buy locally. Big-box stores stock mostly one-inch filters, so four-inch sizes are often special order.
Filterbuy ships fast, with free 2-day delivery to most US states. Need hands-on help? Filterbuy HVAC Solutions serves Southeast Florida (Palm Beach, Broward, Miami-Dade, Treasure Coast) and greater Orlando.
Americans spend about 90% of their time indoors.
Indoor concentrations of some pollutants run 2 to 5 times higher than typical outdoor levels.
Your HVAC filter is the only device treating air in every room.
Source: U.S. EPA, Report on the Environment: Indoor Air Quality (May 2026).
A clean filter cuts an air conditioner's energy use by 5% to 15%.
A loaded filter restricts airflow.
The system then runs longer to reach the same temperature.
Source: U.S. Department of Energy, Energy Saver, Save Money and Stay Cool.
Nearly 28 million Americans have asthma, about 8% of the population.
AAFA names pet dander, dust mites, and mold among common indoor triggers.
If someone in your home has asthma or allergies, talk to their doctor about managing indoor triggers.
Source: Asthma and Allergy Foundation of America, Asthma Facts (April 2026, from CDC National Health Interview Survey data).
MERV efficiency figures elsewhere on this page come from the EPA's published MERV table, derived from ANSI/ASHRAE Standard 52.2. The EPA does not certify or recommend particular filter brands.
A Filterbuy 16x20x4 filter lasts 6 to 9 months across all three MERV ratings, since the 90-day rule applies to one-inch filters. Shorten that for multiple pets, asthma, or wildfire smoke, and replace any filter that looks heavily soiled.
A Filterbuy 16x20x4 measures 15.50" × 19.50" × 3.63". Sizes differ by brand. Filtrete's is 15.88" × 19.88" × 4.31", so check dimensions before switching brands.
MERV 8 is the standard choice for most homes, MERV 11 is built for allergy sufferers and handles pets and pollen, and MERV 13 is our optimal tier for smoke. Check your HVAC manual to confirm which rating your system takes.
Most people find theirs in the standard list. If yours isn't there, we cut custom sizes to the eighth of an inch, so send the measurements and we'll make it.
MERV (Minimum Efficiency Reporting Value): The national consensus scale for how well a filter captures airborne particles, set by ANSI/ASHRAE Standard 52.2. Homes typically use 8 to 13.
Nominal size: The ordering name printed on the frame. The cut is smaller by design.
Actual size: The cut spec. A Filterbuy 16x20x4 measures 15.50" × 19.50" × 3.63".
MPR / FPR: Proprietary rating scales, MPR from 3M and Filtrete, FPR from Home Depot. Neither is MERV, so equivalents are approximate.
Filter bypass: Air slipping around a filter's edges instead of through the media, which defeats filtration at any MERV rating.
AQI (Air Quality Index): The EPA scale for outdoor air pollution. Above 100 is unhealthy for sensitive groups.
A visual walkthrough of the key points covered above.
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