How to Measure Your Filter
Steps 1 & 2
Measuring Length and Width (L x W). (If your filter is not a square, the smallest measurement goes first).


Step 3
Measure the thickness (Depth) of your filter from front to back.

Step 4
Put Your measurements together (L x W x D).

Actual Size
A filter’s true dimensions.
Example: 19.75” x 19.75” x 1”
Nominal Size
Rounded numbers used by manufacturers.
Example 20” x 20” x 1”
View Detailed InstructionsAbout 18x20x1 Air Filter
The Aerostar 18x20x1 pleated air filter delivers clean air by replacing your air system’s vent intake filter. Designed to work with most home and office AC and furnace systems with compatible intake vent sizes, filtering out dust, pollen, bacteria, and other airborne particles. Great indoor air quality is as easy as changing your air filter to Aerostar.
Fights lint, dust mites, mold spores, pollen, pet dander, and dust.
Every 60-90 DaysQualifies for Free Shipping
Pleated MERV 8 Media
Comparable to MPR 600 and FPR 5
Designed for Superior Filtration Efficiency
Made with electrostatically charged synthetic material that draws and captures allergens between 3 - 10 microns, including lint, dust mites, mold spores, pollen, pet dander, and dust.
Improve Indoor Air Quality
Protect your family and loved ones with clean indoor air quality at home. Aerostar filters are a simple and cost effective step towards a healthier home environment, free of airborne allergens and particles that can trigger various allergy and asthma symptoms.
Improve Efficiency and Reduce Cost
An Aerostar furnace air filter helps keep your HVAC unit working efficiently by removing dirt and reducing strain on the motor. When your unit runs properly, it consumes less energy, requires less maintenance and will have a longer life. These factors will have an impact on your utility bill and maintenance costs. It is recommended that you change the filter every 60 to 90 days during normal times of year but increase frequency to 30 days during peak summer and winter months when your unit is working the hardest.
About Aerostar Furnace Air Filters
Aerostar filters are manufactured in the USA by Filtration Group, a world-leading manufacturer and supplier of filtration solutions for residential, commercial and industrial applications. The Aerostar brand is known for constantly innovating and improving their technology to help make filtration more efficient, effective and environmentally friendly every day.
About MERV, MPR and FPR Rating
The three rating systems were created by different organizations. MERV is the domestic and international Industry Standard rating system established by the American Society of Heating, Refrigerating, and Air Conditioning Engineers. The other two rating systems were created by 3M and The Home Depot, but all are rating the same filter.
MERV Rating (Minimum Efficiency Reporting Value): As you have already learned, the MERV Rating is the primary rating system used in the industry, both domestically and internationally. Established by the American Society of Heating, Refrigerating, and Air Conditioning Engineers, MERV rates a filter’s ability to capture and hold particles and pollutants.
MPR (Micro-Particle Performance Rating): MPR Rating is a rating system developed by 3M. It rates the manufacturer’s Filtrete product line and their ability to capture airborne particles smaller than 1 micron.
FPR (Filter Performance Rating): FPR Rating is a rating system developed by The Home Depot for brands sold through their stores, including Honeywell. It utilizes a color code and number scale (4 to 10) that closely resembles the MERV rating.
What is a MERV Rating?
MERV ratings let you know the efficiency and level of filtration that an air filter can handle under normal circumstances. The higher the MERV rating, the finer the particles are that are filtered our of the air in your home. Many air filter retailers use MERV or a similar rating to rate their air filters.

About MERV, MPR and FPR Rating

MERV Rating is the primary rating system used in the industry, both domestically and internationally. Established by the American Society of Heating, Refrigerating, and Air Conditioning Engineers, MERV rates a filter’s ability to capture and hold particles and pollutants.

MPR Rating is a rating system developed by 3M. It rates the manufacturer’s Filtrete product line and their ability to capture airborne particles smaller than 1 micron.

FPR Rating is a rating system developed by The Home Depot for brands sold through their stores, including Honeywell. It utilizes a color code and number scale (4 to 10) that closely resembles the MERV rating.
FAQs
Created to improve indoor air quality, an 18x20x1 filter with a high MERV rating removes microscopic particles, including bacteria, pollen, mold spores, and smoke. Newer HVAC models work well with these filters, but certain older systems may struggle with reduced airflow. If performance declines, switching to a filter with a slightly lower MERV rating can prevent strain without overloading your system.
To achieve the best performance, your HVAC system needs to use a filter that balances airflow and removes airborne particles. An 18x20x1 filter with a higher MERV rating can improve filtration, but if resistance is too high, your HVAC unit might have to work harder and use more energy. Checking the specifications of your system helps determine which filter is compatible to use.
Household conditions factor into how long an 18x20x1 furnace filter is effective. Most filters last about 60 to 90 days, although pet hair, dust, and smoke can shorten their life. Periodically examining your filter to see if it's clogged or discolored can help maintain air flow and ensure your system keeps running smoothly.
To achieve efficient HVAC performance and cleaner air, you need a filter with the power to capture various types of pollutants. Ensuring you pick the right filter for your HVAC unit will create smooth air circulation while protecting your system, reducing the chance of needing expensive repairs, and improving air quality. Factory Direct Filters offers a wide variety of MERV rated 18x20x1 filters that help balance air quality and HVAC efficiency. The amount of air purification you need and whether the filter is compatible will determine which MERV rating you select.
You’ll need to assess how much air filtration you need when you’re selecting between MERV rated air filters. Picking a MERV rated filter that matches your HVAC system’s capacity and specifications is important for maintaining efficiency and longevity. You want to purchase a filter that provides the right amount of filtration for your home without compromising performance. Either a MERV 8 18x20x1 air filter or a MERV 11 18x20x1 air filter will trap common household pollutants and both are suitable for most residential HVAC systems. If you select a MERV 13 18x20x1 air filter, it will provide hospital-grade filtration.
A properly fitted filter reduces your exposure to harmful irritants that may aggravate asthma and allergies. Using a high-quality 18x20x1 AC filter prevents contaminants like dust, mold spores, pollen, and pet dander from circulating around your home. A filter with a higher MERV rating purifies your air, reduces allergy triggers, and minimizes health conditions, supporting better respiratory health and breathing conditions.