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Home / Air Filter Sizes / 18x20x1

18x20x1 Air Filter

Actual Size 17.5 x 19.5 x 0.75-Inches Actual size info The nominal size is the size rounded to the closest whole or half an inch. The actual size is the precise physical size of the filter. Learn more.

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18x20x1

Actual Size 17.5x19.5x0.75

FILTERS
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Nominal Size 18x20x1
Actual Size 17.5x19.5x0.75
17.5"
19.5"
0.75"
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Filter Description

  • Filter size: 18x20x1
  • SKU: FK18x20x1-M8
  • Suitable for: Both HVAC units and Furnaces
  • Actual Size: 17.5 x 19.5 x 0.75"
  • 1-Inch Thick Filter
  • MERV 8 Filter Rating
  • Protection From: Pollen, Dust, Mold, and Dust Mites.
  • Residential / Commercial Use
  • MPR Rating: MPR 600
  • FPR Rating: FPR 4-5
  • Captured Particle Size: 3-10 Microns
  • Capacity: Standard Capacity
  • Shipping: Within 3-10 days depending on size and quantity
DeliveryFree Delivery: Ships in 24 Hours
MADE IN USA

18x20x1 Air Filter

Actual Size 17.5 x 19.5 x 0.75-Inches Actual size info The nominal size is the size rounded to the closest whole or half an inch. The actual size is the precise physical size of the filter. Learn more.

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Filter Quality
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DeliveryFree Delivery: Ships in 24 Hours
30-Day Money-Back Guarantee

If for any reason you are not satisfied with your purchase, return it to us within 30 days, and we'll make it right.

INCLUDED IN YOUR ORDER

  • Made in USA
    Made in USA

    All filters are designed and assembled in the U.S.A.

  • Premium Quality
    Premium Quality

    We design and manufacture our filters right here in the U.S.A.

  • Secure Payments
    Secure Payments

    Your information is always secure and encrypted during checkouts.

What MERV should I choose?

Filter King makes a variety of MERV-rated standard filters for all commercial and residential HVAC systems, and we can also manufacture custom-sized filters on request.

Scroll right to see more
Pollen
Dust
Mold
Dust Mites
Bacteria
Virus
Odor
MERV 8
MERV 8

Filters out 90% of airborne particles

Comparable to MPR 600 & FPR 4-5
Pollen
Dust
Mold
Dust Mites
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Bg
Bg
MERV 11
MERV 11

Filters out 95% of airborne particles

Comp. to MPR 1000-1200 & FPR 6-7
Pollen
Dust
Mold
Dust Mites
Bacteria
Bg
Bg
MERV 13
MERV 13

Filters out 98% of airborne particles

Comp. to MPR 1500-1900 & FPR 8-10
Pollen
Dust
Mold
Dust Mites
Bacteria
Virus
Bg
CARBON
CARBON

Filters out 98% of airborne particles

Comparable to MPR 600 & FPR 4-5
Pollen
Dust
Mold
Dust Mites
Bacteria
Bg
Odor
Still not sure? Read our MERV rating filter guide.

Ordering Guide for First-Time Buyers

Buying your first 18x20x1 air filter? We make it simple to get exactly what you need:

Step 1: Check Your Filter Size

Before ordering, make sure you’ve selected the correct size for your system.

Simply check the size printed on the frame of your current filter.

If you don’t see it, measure your filter housing directly.

Note: 18×20×1 air filters measure slightly smaller than the nominal size. Exact measurements are 17.5" x 19.5" x 0.75" to ensure proper fit.

Step 2: Select Your Filtration Level

Choose the MERV rating that matches your air quality needs:

  • MERV 8: Best for basic household use, capturing 90% of large particles like dust, pollen, and lint.
  • MERV 11: Ideal for homes with pets or mild allergy concerns. Provides a higher level of filtration, capturing smaller irritants, air pollution, and allergens.
  • MERV 13: Maximum protection against fine particles, smoke, and bacteria.
  • Carbon Filter: Combines MERV 8 filtration with odor-eliminating carbon. Ideal for reducing household odors like lingering smoke and cooking smells.

Step 3: Place Your Order

Make the most of your purchase with Filter King:

  • Enjoy free shipping anywhere in the U.S.
  • Save with multi-pack orders
  • Set up auto-delivery to never run low
  • Set up a business account for wholesale pricing on bulk orders

Whether you need AC filters 18x20x1 or furnace filters 18x20x1, Filter King makes it easy to get the right fit every time. Remember to install your filter correctly for optimal performance. 

Fit Guarantee for 18x20x1 Filters

Buying air filters online can raise a big question: will it fit? With Filter King, the answer is yes, every time.

Our 18x20x1 filters are premium quality, USA-made, and precision-cut for a perfect fit. That means:

  • No gaps or forcing into place
  • Snug, secure installation that seals tightly in the return vent
  • Consistent airflow and reliable performance for your HVAC system

Whether it’s an AC or furnace application, you’ll get a filter that fits and works exactly like it should from day one.

Our filters are backed by a 30-day money-back guarantee. If you’re not satisfied with fit or performance, we’ll make it right.

Filter Lifespan and Maintenance Tips

Our 18x20x1 filters last 3 months with typical household use. But you may need more frequent changes if you have:

  • Pets in the home
  • Family members with allergies or asthma
  • A smoking household
  • Construction or renovation nearby
  • High outdoor pollution levels
  • Commercial or high-traffic spaces

Pro Tip: Check your filter monthly for visible dust and debris buildup. That means it's time for a replacement—even if it hasn't been 3 months.

Read more about how long air filters last.

To stay ahead, set calendar reminders and subscribe for auto-delivery when you place your order.

FK Lion ALWAYS THE RIGHT FILTER GUARANTEE

Selecting the Appropriate Air Filter Size

Air filters come with both a nominal size and an actual size. The nominal size is typically rounded up to the nearest whole or half inch and is printed in a larger font.

Nominal Size

The nominal size is typically rounded up to the nearest whole or half inch and is printed in a larger font.

18x20x1

Actual Size 17.5x19.5x0.75

Actual Size

The actual size represents the precise physical dimensions of the filter and is printed in a smaller font.

Nominal Size 18x20x1
17.5"
Filter Blank
19.5"
0.75"
Actual Size is 17.5x19.5x0.75

Measuring

If your previous filter lacks dimensions printed on the frame,
take a tape measure and record the
length x width x depth.

LinkLearn more about filter sizes

Key Features

MERV 8 Air Filters stand out as the preferred choice among various MERV ratings. They significantly enhance indoor air quality while optimizing the efficiency of your HVAC system, effectively eliminating up to 90% of airborne contaminants while maintaining optimal airflow.

Industry Standard Board Frames

Paperboard air filter frames are cut to fit any air filtration system, and their purposes is to hold HVAC filters in place. They consist of a weave that traps and absorbs the particles caught in the incoming airflow.

Air Filter

Pleated Air Filters

This innovative design ensures that our filters last three times longer than fiberglass counterparts while effectively capturing harmful particles, ultimately enhancing air quality for everyone.

Protects Against

  • Pollen
    Pollen
  • Dust
    Dust
  • Mold
    Mold
  • Dust Mites
    Dust Mites
  • Bacteria
    Bacteria

Pleated Vs Fiberglass?

A pleated air filter's media follows a folding pattern, which creates increased surface area, and in turn, allows more air flow while maintaining the quality of air. On the other hand, a fiberglass filter has a minimal surface area, and furnace filters out larger particles
like dust and lint and is not very effective.

Pleated Filter
Pleated Filter
  • Larger surface area captures more particles
  • Less replacement frequency
  • Average lifespans of 3-12 months
  • Higher MERV rating 8-13
  • Higher quality, sturdy and durable
Fiberglass Filter
Fiberglass Filter
  • Smaller surface area captures less particles
  • More replacement frequency
  • Average lifespans of 1-2 months
  • Lower MERV rating 2-4
  • Lower quality, flimsy and porous

How often should you change your filter?

Filter King AC & furnace filters aren’t the typical fiberglass filters that need to be replaced every 30 days. Our filters can typically be used for 3 months without change.

You should change your filter more frequently if you notice:

  • Household dust build-up
  • Higher energy bills
  • The air isn’t cooling as is used to
  • There’s more dust near the air vents
  • A dirty filter surface
  • Burning smells near your HVAC system

How to install your air filter?

Installation couldn't be easier. Every filter features an airflow arrow printed on its side. It's crucial to align this arrow with the direction of the air when inserting the filter into your furnace or central air return ducts.

  • Step 1
  • Step 2
  • Step 3
  • Step 4

Why replacement Air Filters?

MERV 8 filters stand out as the preferred choice among various MERV ratings. They significantly enhance indoor air quality while optimizing the efficiency of your HVAC system, effectively eliminating up to 90% of airborne contaminants while maintaining optimal airflow.

Clean Air

Clean Air for you and
Your Family

Air filters serve 3 critical roles in your central air system that contribute to the health and comfort of residents and customers. Air filters remove harmful pollen, dust, dander, smoke. and bacteria, so they don't circulate throughout your home or commercial space from a dirty filter.

Clean Air

Efficient Heating and Lower Costs

Regularly changing your furnace filters isn't just about maintaining your heating system—it's about saving money and enhancing efficiency. A clean filter ensures your furnace operates smoothly, reduces energy consumption, and minimizes heating costs.

By keeping your system free from dust and debris buildup, you prolong its lifespan and avoid costly repairs or replacements. Consistent filter maintenance is a simple yet effective way to keep your furnace running efficiently and economically.

Need a reference?

We've got plenty.

View all reviews

Similar Sizes

4 Pack of 18x18x1 Air Filter 18x18x1 4 Pack of 18x19x1 Air Filter 18x19x1 4 Pack of 18x21x1 Air Filter 18x21x1 4 Pack of 18x22x1 Air Filter 18x22x1 4 Pack of 18x24x1 Air Filter 18x24x1 4 Pack of 18x25x1 Air Filter 18x25x1

Different Thickness

4 Pack of 18x20x0.5 Air Filter 18x20x0.5 4 Pack of 18x20x2 Air Filter 18x20x2 4 Pack of 18x20x4 Air Filter 18x20x4

FAQs

Check the label on your existing filter, furnace manual, or measure the filter compartment for exact dimensions.

Yes, higher MERV ratings filter smaller particles more effectively.

Filters with activated carbon or charcoal can reduce pet odors effectively.

HEPA or MERV 13+ filters can help reduce airborne viruses, potentially lowering COVID-19 transmission risk.

Activated carbon or charcoal filters effectively reduce chemical odors.

Need help deciding?

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If the measurements on your current filter match the ones mentioned above, then you have identified your filter size.

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If the measurements on your current filter match the ones mentioned above, then you have identified your filter size.

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Guarantee

Satisfaction guaranteed

If the measurements on your current filter match the ones mentioned above, then you have identified your filter size.

Learn more

About Filter King

Filter King is an air filter manufacturer that specializes in making high quality air filters for a variety of purposes. The company has been in business for over 4 years and has already established a strong reputation for making air filters that are both effective and affordable.

Filter King air filters are designed to remove airborne particles such as dust, pollen, and smoke from the air, making them an ideal choice for people with allergies or respiratory problems. Filter King air filters are used in homes, office buildings, and hospitals across the country.

The company's air filters are also used in a variety of industries, including food processing, pharmaceuticals, and manufacturing. The company offers a wide range of air filters sizes, including models that are custom size, designed exactly for your need.