${{ totalOrderSum() }}
- +

Home / Air Filter Sizes / 16x21.5x4a

16x21.5x4 Air Filter

Actual Size 16 x 21.5 x 3.75-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.

  • 1
  • 2
  • 3
  • 4
  • 5
{{ yotpoProductReviewsCount.total_review }} {{ yotpoProductReviewsCount.total_review > 1 ? 'Reviews' : 'Review'}}
Product Image 1 Product Image 1 Product Image 1 Product Image 1
16x21.5x4

Actual Size 16x21.5x3.75

FILTERS
Product Image 2 Product Image 2 Product Image 2 Product Image 2
Nominal Size 16x21.5x4
Actual Size 16x21.5x3.75
16"
21.5"
3.75"
Product Image 3 Product Image 3 Product Image 3 Product Image 3
Product Image 4 Product Image 4 Product Image 4 Product Image 4
Product Image 5 Product Image 5 Product Image 5 Product Image 5
  • Product Image 1 Product Image 1 Product Image 1 Product Image 1
  • Product Image Thumb 2 Product Image Thumb 2 Product Image Thumb 2 Product Image Thumb 2
  • Product Image Thumb 3 Product Image Thumb 3 Product Image Thumb 3 Product Image Thumb 3
  • Product Image Thumb 4 Product Image Thumb 4 Product Image Thumb 4 Product Image Thumb 4
  • Product Image Thumb 5 Product Image Thumb 5 Product Image Thumb 5 Product Image Thumb 5

Filter Description

  • Filter size: 16x21.5x4
  • SKU: FK16x21.5x4-M8
  • Suitable for: Both HVAC units and Furnaces
  • Actual Size: 16 x 21.5 x 3.75"
  • 4-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

16x21.5x4 Air Filter

Actual Size 16 x 21.5 x 3.75-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.

  • 1
  • 2
  • 3
  • 4
  • 5
{{ yotpoProductReviewsCount.total_review }} {{ yotpoProductReviewsCount.total_review > 1 ? 'Reviews' : 'Review'}}
Filter Quality
Help me choose
Select Quantity Discount
${{ totalOrderSum() }}
${{ pricePerQuantity() }}/Filter
SAVING {{ savePercent()}}%
SAVING {{ savePercent()}}%
- - + +
${{ money(priceWithoutDiscount()) }} ${{ totalOrderSum() }}
You saved ${{ money(savePrice()) }}
  • QTY
    EACH
    SAVINGS
  • {{ index + 1 }} 6-11 12+
    ${{ price }}
    {{ savePercentByQuantity(price, index+1) }}%
{{ filter_count }} x 16x21.5x4 Air Filters
${{ totalOrderSum() }}
${{ money(priceWithoutDiscount()) }}
${{ pricePerQuantity() }}/Filter
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
Bg
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.
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.

16x21.5x4

Actual Size 16x21.5x3.75

Actual Size

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

Nominal Size 16x21.5x4
16"
Filter Blank
21.5"
3.75"
Actual Size is 16x21.5x3.75

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 16x20x4 Air Filter 16x20x4 4 Pack of 16x21x4a Air Filter 16x21x4 4 Pack of 16x22x4a Air Filter 16x22x4 4 Pack of 16x22.25x4a Air Filter 16x22.25x4 4 Pack of 16x24x4 Air Filter 16x24x4 4 Pack of 16x25x4 Air Filter 16x25x4

Different Thickness

4 Pack of 16x21.5x0.5a Air Filter 16x21.5x0.5 4 Pack of 16x21.5x1a Air Filter 16x21.5x1 4 Pack of 16x21.5x2a Air Filter 16x21.5x2

FAQs

It's not recommended; thinner filters may allow more unfiltered air to pass, reducing air quality.

Consider custom-made filters or contacting the manufacturer for specific recommendations.

Usually yes, MERV 16 is typically for hospital or commercial settings and might overly restrict airflow in home systems.

No, filters don't expire, but keep them sealed and dry to maintain effectiveness.

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

Need help deciding?

Chat

Chat with us

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

Ask away
Reviews

Read real reviews

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

LinkGo to reviews
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.