Best 13x24x1 MERV 13 Furnace & HVAC Air Conditioner Filters

Author: Michelle Wan, Brand Manager and Air Quality Writer  |  Reviewer: David Clark, Licensed HVAC Technician  |  Published and updated August 7, 2026

A 13x24x1 MERV 13 air filter is a one-inch pleated HVAC filter that captures fine particles like smoke, bacteria, pollen, and pet dander in systems built for a 13-by-24-inch return. Filterbuy cuts this size on its own U.S. lines, to a true 13" x 24" face rather than the undersized dimensions standard filters use. Filterbuy builds it because stores mostly do not, and because the homeowners who need it kept asking.

TL;DR

The best 13x24x1 MERV 13 air filter is the Filterbuy pleated MERV 13, built in Filterbuy's U.S. plants and shipped free. Measure your filter before ordering. This is a non-standard size; the usual rounding rule does not apply.

Key Takeaways

• 13x24x1 is cut to a true 13" x 24" face. Standard sizes like 12x24x1 measure about 11 3/8" x 23 3/8". Do not round up.

• MERV 13 captures at least 50% of 0.3–1.0 micron particles and 85% of 1.0–3.0 micron, per ANSI/ASHRAE 52.2. The EPA recommends it, provided the filter is replaced frequently.

• Big-box shelves rarely carry 13x24x1. Filterbuy builds it to order in the USA, which is why odd sizes cost more per filter.

• Multi-packs cut the per-filter price by roughly half, and Auto Delivery takes another 5%.

Is 13x24x1 Really the Size You Need?

Only if it measures a true 13 by 24 inches. Most sizes are nominal: the printed number is rounded up and the filter cut 3/8" to 5/8" smaller. 13x24x1 is not. The habit that gets you the right standard filter gets you the wrong odd size.

Sizing questions are what Filterbuy's support team fields daily, enough that we built our measuring guide out of those calls. Nearly all trace to one assumption: the printed number exceeds the filter.

Depth is a nominal 1" measuring roughly 3/4", as on every 1-inch pleated filter.

The Three-Step Rule for Odd Sizes

1. Read the size printed on your filter. If it says 13x24x1, order 13x24x1.

2. If the print has worn off, measure the filter or slot opening: length, width, depth.

3. Match it against the actual-size column above rather than rounding up. 13 3/8" x 23 3/8" is a 14x24x1; 12 1/2" x 24 1/2" is a 13x25x1. Only a true 13" x 24" is this filter.

Unsure? Filterbuy's free exchange policy sends a better size free, and its custom air filter builder cuts to your measurements.

“Most filter advice quietly assumes you own a standard size. When you don't, the usual rule, measure and then round up, is the exact thing that gets you the wrong filter. On 13x24x1 the number on the label is the number you measure. That is the whole trick, and almost nobody says it out loud.”

What a MERV 13 Filter Actually Captures

MERV 13 captures smoke, bacteria, mold spores, pollen, and fine dust, and sits at the top of what a typical residential blower can handle. Here is what the standard requires at each particle size.

Minimum efficiencies defined by ANSI/ASHRAE Standard 52.2.

Those are floors, not ceilings, which is why Filterbuy publishes the ASHRAE thresholds rather than one headline percentage. Filterbuy rates its own MERV 13 media at 98% of airborne particles, comparable to MPR 1900 and FPR 10.

What MERV 13 does not do: no pleated filter removes gases. Cooking odors, VOCs, and carbon monoxide pass through at any MERV rating. Those need activated carbon or, for carbon monoxide, a detector.

13x24x1 MERV 8 covers household dust and 13x24x1 MERV 11 adds smoke and smog. MERV 13 adds bacteria and the fine particulate in wildfire smoke, which is why the EPA advises at least MERV 13, or as high as your system allows.

Will MERV 13 Restrict Airflow in a 1-Inch Slot?

Not in most homes, but with one condition. Higher-MERV media creates more resistance, and a 1-inch filter has less area to spread it across than a 4-inch. Filterbuy builds this size with a pleat density and dual-wire backing that keep pressure drop within residential tolerances, but a clogged MERV 13 restricts airflow far more than a clogged MERV 8. Two cases warrant a check: older furnaces with PSC blower motors, and systems already showing airflow complaints. Have a technician measure static pressure first. If it cannot support MERV 13, 13x24x1 MERV 11 is the safer step up.

Should Your 13x24 Slot Take a 1-Inch or a 2-Inch Filter?

If your rack accepts two inches, buy the two-inch. Filterbuy cuts 13x24 in both depths, and the thicker filter is better wherever it fits. Measure your slot depth before assuming one inch.

A 13x24x2 MERV 13 carries roughly twice the media behind the same face. That buys three things:

• Lower pressure drop at the same MERV 13 rating, with more surface area to cross.

• Longer service life, since it loads more slowly.

• The same exact-cut face, at an actual depth of 1 3/4".

A 2-inch filter will not fit a 1-inch slot; forcing it bends the frame and opens gaps. If your slot measures about one inch, the filter on this page is the right one. The airflow penalty people blame on MERV 13 is mostly a depth problem, not a rating problem.

Replacement Schedule, Pack Sizes, and Cost Per Filter

Replace every 90 days normally, every 60 with pets or allergies, every 30 in smoke regions. Frequent replacement is the EPA condition for running a higher-MERV filter. Because Filterbuy builds 13x24x1 to order, buying ahead matters more than for a common size, and packs offset the odd-size premium. Auto Delivery saves a further 5% per order.

Coverage assumes a 90-day replacement schedule. Auto Delivery saves an additional 5%.

Also in this size: 13x24x1 MERV 8 for basic dust, and 13x24x1 MERV 11 for pets and allergies. See all options on the 13x24x1 air filters, or compare 14x24x1 and 12x24x1 air filters if you measured differently.

Why Buy 13x24x1 MERV 13 Filters From Filterbuy

Because the company that cuts the filter also sells it. Filterbuy makes 13x24x1 on its own lines in Alabama, Florida, Pennsylvania, and Utah, using electrostatically charged pleated media and dual-wire backing that holds pleat spacing under airflow. Shipping and exchanges are free, because odd sizes are where fit goes wrong.

Written by Michelle Wan, Filterbuy's Brand Manager, who works with the production teams at those plants and writes from how these filters are cut and tested. Reviewed for accuracy by David Clark, an EPA-certified HVAC technician.

Supporting Statistics: What Federal Research Says About MERV 13

Three U.S. government findings behind the claims above.

1. High-Efficiency Filters Cut Indoor Particles by Up to 95%

• A MERV 13-16 filter reduces indoor particle concentrations by as much as 95%.

• Most homes ship with MERV 1-4 fiberglass.

• Switching the fan to "On" cuts particles by up to 24%.

Source: EPA Wildfire Smoke Factsheet, Indoor Air Filtration (EPA-452/F-18-005)

For 13x24x1: runtime matters as much as rating.

2. Asthma Affects 8.6% of U.S. Adults and 6.5% of Children

• 8.6% of American adults and 6.5% of children currently have asthma.

• Asthma is the primary diagnosis in roughly 1.4 million ER visits a year.

• Fine particulate is a known trigger.

Source: CDC National Center for Health Statistics, FastStats: Asthma (2024 data, reviewed February 2026)

For 13x24x1: in one household in twelve this is medical, not preference.

3. Heating and Cooling Use Nearly Half of Home Energy

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

• Check the filter monthly in heavy-use months; replace at minimum every three.

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

Source: ENERGY STAR, Heat & Cool Efficiently (joint EPA and Department of Energy program)

For 13x24x1: the 90-day interval above is federal guidance, not a sales schedule.

Frequently Asked Questions

Is a 13x24x1 MERV 13 Filter Good for Allergies and Asthma?

Yes. MERV 13 captures at least 85% of mold spores and bacteria at 1.0–3.0 microns, and 90% of pollen and dander at 3.0–10 microns.

How Often Should I Replace a 13x24x1 MERV 13 Filter?

Every 90 days under normal conditions, every 60 days with pets or allergies, and every 30 days in wildfire or heavy-smog regions. Heavy smoke can load a MERV 13 in weeks rather than months.

Will a MERV 13 Filter Damage My HVAC System?

Not in most modern systems, provided you replace it on schedule. Older units with PSC blower motors should have static pressure measured first.

Where Can I Buy a 13x24x1 MERV 13 Filter?

Rarely on a store shelf. 13x24x1 is a non-standard size. Filterbuy builds it to order in the USA and ships direct, free.

Can I Use a 12x24x1 or 14x24x1 Filter Instead?

No. Both are cut undersized, and air bypasses a filter that does not fill its slot.

Sources and Further Reading

Every claim above traces to one of these.

• How to measure your air filter: why 13x24x1 breaks the rounding rule

• Air filter sizes chart: all 600-plus sizes, nominal and actual

• Best MERV filter for wildfire smoke: why MERV 8 and 11 miss PM2.5

• MERV 13 vs. HEPA for wildfire smoke: why most blowers cannot run true HEPA

• EPA, Guide to Air Cleaners in the Home: the federal recommendation

• EPA, What is a MERV rating?: the scale in plain language

• ANSI/ASHRAE Standard 52.2: the test method behind every MERV number

Glossary

• MERV: Minimum Efficiency Reporting Value, the ANSI/ASHRAE 52.2 scale for filter efficiency.

• MERV 13: Captures at least 50% of 0.3–1.0 micron particles, 85% of 1.0–3.0 micron, and 90% of 3.0–10 micron.

• Nominal Size: The rounded size printed on the frame. Usually larger than the filter itself.

• Actual Size: The filter's true measured dimensions. On 13x24x1 the face matches nominal; depth does not.

• Non-Standard Size: A dimension general retailers do not stock, like 13x24x1.

• Pressure Drop: The airflow resistance a filter adds, measured in inches of water column.

Get Your 13x24x1 MERV 13 Filters, Direct From Our Factory

Confirm your filter measures a true 13" x 24", then choose your pack size. Filterbuy builds it to order in the USA and ships free. Add Auto Delivery to stay on schedule, or browse all MERV 13 air filters from Filterbuy.