16x25x4 Air Filters: Furnace and AC Filters Made in the USA

Nominal 16 x 25 x 4 in  ·  Actual 15.5 x 24.5 x 3.63 in  ·  MERV 8, 11 and 13  ·  Made in the USA

Author: Michelle Wan, Brand Manager and Air Quality Writer, Filterbuy 

Technically reviewed by David Clark, Licensed HVAC Technician, Filterbuy HVAC Solutions

Updated August 12, 2026

TL;DR

A 16x25x4 air filter is a four-inch-deep pleated HVAC filter built for a slot measuring 16 by 25 inches. It is your furnace filter and your air conditioner filter at once, because a home with a central HVAC system runs both through one blower and one slot. The Filterbuy 16x25x4 measures 15.5 x 24.5 x 3.63 inches in MERV 8, 11, and 13, and most homes change it every 90 days.

Key Takeaways

• The nominal size 16x25x4 is what you order. The Filterbuy filter measures 15.5 x 24.5 x 3.63 inches, cut half an inch under nominal so it seats without binding.

• Furnace filter, AC filter, and HVAC filter are the same part in an HVAC system.

• Media cabinets branded Honeywell, Carrier, Bryant or Aprilaire take 5-inch and 6-inch filters, not 16x25x4.

• Filterbuy 4-inch filters carry 8 pleats per foot against 14 on our 1-inch, and it’s that extra depth that makes a 4-inch last about 90 days.
  
  

What Is A 16x25x4 Air Filter?

A 16x25x4 air filter is a pleated, disposable HVAC filter for a slot roughly 16 by 25 inches and 4 inches deep, and Filterbuy makes it in MERV 8, MERV 11 and MERV 13. The figure itself is the nominal size printed on the frame.

Will A 16x25x4 Filter Fit My Furnace Or Air Conditioner?

Finding your size takes about a minute. Slide the old filter out and read the size printed along the frame, and if there isn’t one in there, measure the slot instead. If it comes to roughly 16 by 25 inches and 4 inches deep, a 16x25x4 is your filter.

1. Turn the system off at the thermostat and open the filter access door.

2. Read the size off the old filter’s frame, or measure the opening to the nearest eighth of an inch.

3. Compare your measurements with the actual sizes in the chart to find your match.

4. If the filter sits in a boxed cabinet, check it for a model sticker. A code beginning FC100A or ExPxx, or an Aprilaire model number, means your system takes a deeper media filter.

Actual sizes from manufacturers' published specifications, August 2026. Measure your slot before ordering. Links to the correct 5-inch and 6-inch filters are directly below this table.

If your cabinet is one of these, we make the filter that fits it. Our Honeywell 16x25x5 replacement filters are cut to 15.75 x 24.75 x 4.38 to match that cabinet. There are also Carrier and Bryant 16x25x5 filters and Aprilaire 2200 filters in 20x25x6. If your slot lands on an odd fraction, we cut a custom air filter to your numbers.

Honeywell, Carrier, Bryant, Aprilaire, and Lennox are trademarks of their respective owners. Filterbuy filters are compatible replacement options designed to fit select systems from these brands. Filterbuy is an independent manufacturer and is not affiliated with or endorsed by these companies. 

That half-inch of clearance is deliberate. It’s what lets the filter slide into the slot and still seal against it. The clearance we cut is our own, though, and other manufacturers use different ones, so read the actual dimensions on any frame before you switch brands.

We publish other manufacturers’ numbers next to our own, including the rows where we come off worst. You cannot check a fit nobody told you about.

Which MERV Rating Is Right For Your Home?

Filterbuy makes the 16x25x4 in MERV 8, MERV 11 and MERV 13. MERV 8 is the standard choice for most homes. MERV 11 is our tier for allergy sufferers, and it’s the one to pick if you’ve got pets or pollen coming in. MERV 13 is the optimal tier for smoke. If odors are what you’re dealing with, the Odor Eliminator carbon filter handles those instead.

MPR and FPR are third-party rating systems developed by other companies, shown here for comparison only.

MERV stands for Minimum Efficiency Reporting Value, which measures how much airborne particulate a filter catches. The higher the number, the more it captures.

Before you order, check your HVAC manual to confirm which filters your system takes. It’s the same quick check as confirming your size, and it takes about a minute. If you have questions about allergies, asthma, or anything else health-related, talk to a qualified professional.

How Often Should You Change A 16x25x4 Furnace Filter?

Every 90 days in a typical home. A 16x25x4 holds far more dust than a 1-inch filter, which is why it runs roughly three times as long. Shorten that whenever your home is harder on a filter than average.

Check the filter monthly in any season that loads it faster.

No replacement schedule knows how hard your own system works. Ninety days assumes typical running time, and a system running most of a hot August will load a filter far faster than one drifting through a mild spring. Treat the interval as a starting point and check the filter monthly.

To judge it without a calendar, hold the filter up to a light. If none comes through the pleats, it’s past due. Grey on the intake side isn’t a fault; that’s the filter doing its job. When you fit the new one, write the date on the frame in marker. It’s the cheapest reminder there is.

Is A 16x25x4 Better Than A 16x25x1?

For a system with a 4-inch slot, yes. A 16x25x4 gives you 3.63 inches of media depth against 0.75 inches on a 16x25x1, so it holds far more dust and lasts roughly three times as long. You do need a 4-inch slot for it, though, and you can’t stack 1-inch filters to make up the depth.

Most people assume more pleats means more filter. Our 1-inch filters actually carry 14 pleats per foot while our 4-inch carry only 8, because each of those pleats is so much deeper. It’s the depth that does the work, so that’s the number worth shopping on.

How Much Do 16x25x4 Air Filters Cost?

A single Filterbuy 16x25x4 is $33.99, six work out to $15.99 each, and twelve or more come down to $15.08. Filterbuy makes and ships its own filters, so no distributor margin sits inside that price.

Auto-delivery takes a further 5% off any quantity.

Six filters is about eighteen months at the 90-day interval, and Air filter auto-delivery sends the next set on your schedule with another 5% off.

Where To Buy 16x25x4 Air Filters Near You

Big-box stores stock 16x25x4 thinly, because shelf space goes to the four most common 1-inch sizes. Filterbuy cuts, pleats and frames this size to order in our own US plants, with fast, free 2-day delivery to most US states. If you need one today, call your local store ahead and ask for the actual dimensions.

Supporting Statistics

From federal and public-health sources.

1. You breathe indoor air roughly 22 hours a day

• Americans spend about 90% of their time indoors.

• Some pollutants run 2 to 5 times higher indoors than out.

• Your filter cleans the air your household breathes.

Source: US Environmental Protection Agency, Indoor Air Quality, Report on the Environment.

2. 44% of Americans live where the outdoor air fails

• 152.3 million live in counties graded F for ozone or particle pollution.

• 75.9 million fail the year-round particle standard.

• Particle pollution is the kind of airborne particulate a pleated filter is rated to capture.
  

Source: American Lung Association, State of the Air 2026, Key Findings.

3. Heating and cooling is about half your home energy use

• Nearly half the energy used in a US home goes to heating and cooling.

• A dirty filter slows airflow and makes the system work harder.

• Airflow problems can cut system efficiency by up to 15 percent.

• Changing on schedule is the cheapest efficiency step in the house.
  

Source: ENERGY STAR, Heat & Cool Efficiently.

Frequently Asked Questions

What is the actual size of a 16x25x4 air filter?

A Filterbuy 16x25x4 measures 15.5 x 24.5 x 3.63 inches, cut half an inch under nominal on length and width so it slides in without binding. Other manufacturers cut theirs differently, so read the actual size on the frame before you switch. Our full air filter size chart lists nominal against actual for every size we make.

Will a 16x25x4 filter fit a Honeywell, Carrier or Aprilaire cabinet?

No, in almost every case. The 16 by 25 Honeywell media filter is the FC100A1029, a 16x25x5, as is the Carrier and Bryant EZ Flex ExPxxFIL0016, while the Aprilaire 2200 and 2250 take filter 201, a 20x25x6. All three cabinets are built around 5-inch and 6-inch filters, so a 3.63-inch filter leaves a gap that lets unfiltered air bypass the media. Filterbuy makes exact-fit Honeywell 16x25x5 replacement filters at 15.75 x 24.75 x 4.38 inches.

Are furnace filters and AC filters the same thing?

Yes. In a forced-air home, the furnace and the air conditioner share one blower, one duct system and one filter slot, so furnace, AC and HVAC filter size all mean the same thing.

What does MERV 13 give me that MERV 11 doesn’t?

MERV 13 is our optimal tier and it’s rated hospital grade. It captures 98% of airborne particles against 95% for MERV 11, and it’s the tier we point smoke at. MERV 11 is built for allergy sufferers. Check your HVAC manual to confirm which filters your system takes, the same way you’d confirm the size.

Which way does the arrow on a 16x25x4 filter point?

Toward the furnace or air handler, following the direction the air travels, which usually means away from the return duct. If you can’t tell, hold a tissue near the open slot with the system running.

Will a higher MERV rating get rid of a smell?

No, and it’s the upgrade we most often talk people out of. MERV rates solid particulates, not gases, so odor molecules pass straight through whether the filter is rated 8 or 13. The American Lung Association points to activated carbon instead, which adsorbs those compounds. If your problem is pet smell, cooking or smoke rather than dust, Filterbuy’s activated carbon Odor Eliminator filters are the change worth making.

Where can I find 16x25x4 air filters on sale?

Buying in quantity is where the discount sits: a six-pack works out at $15.99 each against $33.99 for one. Because we manufacture what we sell, that price stands all year. It isn’t a seasonal promotion.

Glossary

Nominal size. The rounded measurement printed on an air filter frame, written as length x width x thickness. Nominal size is what you order.

Actual size. The true measured dimensions of the filter. A Filterbuy 16x25x4 has an actual size of 15.5 x 24.5 x 3.63 inches.

MERV. Minimum Efficiency Reporting Value, the scale that rates how much airborne particulate a filter captures, defined by ANSI/ASHRAE Standard 52.2.

Pleated filter. A filter whose media is folded into pleats to increase surface area, so it captures far more than a flat fiberglass panel of the same size.

Forced-air system. A heating and cooling system that moves conditioned air through ducts with a blower.

About the Author: Michelle Wan is Brand Manager and Air Quality Writer at Filterbuy and fronts much of the brand’s educational video content. She works with Filterbuy’s U.S. manufacturing teams, so she writes from how filters are built and used rather than from spec sheets.

Reviewed by: David Clark, Licensed HVAC Technician, Filterbuy HVAC Solutions.