What is the air filter number?

An air filter number is a unique identifier that helps you find the right replacement filter for your vehicle or HVAC system. This number is typically printed on the existing filter and indicates the specific size, shape, and other key details needed to ensure a proper fit and optimal performance.

What is an Air Filter Number?

An air filter number is a combination of letters and numbers that provides detailed information about the air filter. This includes the filter's dimensions, such as length, width, and height, as well as its shape, material, and other specifications. By matching the air filter number on your existing filter, you can easily find the correct replacement part that will fit your system perfectly.

Why is the Air Filter Number Important?

• Proper Fit: Using the right air filter number ensures the replacement filter will fit securely in your vehicle or HVAC system, preventing air leaks and maintaining optimal airflow.


• Optimal Performance: Each air filter is designed for specific applications, so the correct number ensures the replacement filter will provide the expected level of filtration and protection for your system.


• Manufacturer Recommendations: Many vehicle and HVAC manufacturers specify the exact air filter number they recommend for their products, so using the correct number helps maintain warranty coverage and system performance.

Knowing and using the right air filter number is crucial for maintaining the health and efficiency of your vehicle or HVAC system.

How to Find the Air Filter Number

The air filter number is typically printed directly on the existing filter, often on a label or sticker. It may also be listed in your owner's manual or on the manufacturer's website. If you can't find the number, you can take the old filter to an auto parts store or HVAC supplier, and they can help you identify the correct replacement.

What are the numbers on an air filter?

The numbers on air filters usually indicate the dimensions of the filter. This includes the length, width, and thickness.

How do I tell what air filter I need?

To find the right air filter, first check the size printed on the existing filter (usually in a width x height x thickness format) or find the size in your HVAC system's manual. If you can't find the dimensions, measure the filter slot yourself, rounding up to the nearest inch for each dimension (e.g., 19.5" x 24.5" x 0.75" becomes 20x25x1). Next, decide on the MERV rating, which indicates the filter's efficiency; a MERV 8 is good for most homes, while higher ratings like MERV 11 or 13 are better for allergies or pet dander. 
This video demonstrates how to find the air filter size from your current filter and how to measure the filter slot if there's no existing filter: 59sFilterTimeYouTube · Oct 25, 2021
1. Find the correct size

• Check the existing filter: The size, often listed as width x height x thickness (e.g., 20x25x1), is usually printed on the filter's cardboard frame. 
• Consult the manual: The correct size and specifications should be in your HVAC system's owner's manual. 
• Measure it yourself: If the information isn't on the old filter or in the manual, use a tape measure to measure the filter's width, height, and depth. 
• Round up: When measuring, round each dimension up to the nearest whole inch to get the nominal size for purchasing (e.g., 19.5" x 24.5" x 0.75" becomes 20x25x1). 
• Check the thickness: Be sure to get the correct thickness (e.g., 1" or 4") to ensure a proper fit and avoid damage or inefficiency. 

This video explains the difference between nominal and actual filter size and how to choose a compatible filter based on its size: 56sKevin KingYouTube · Oct 12, 2020
2. Determine the MERV rating 

• MERV 8: This is a standard, cost-effective rating that is sufficient for most homes. 
• MERV 11 or higher: If you have allergies, asthma, or pets, a higher MERV rating can provide better filtration of particles like dander and pollen. 
• Be aware of system limitations: Filters with very high MERV ratings (above 13) can restrict airflow, potentially straining your HVAC system. Ensure your system can handle a higher-efficiency filter before purchasing one. 

You can watch this video to understand what MERV ratings mean and how to choose the right one for your needs, including the potential impact of high MERV ratings on your HVAC system: 1mLearned From DadYouTube · Sep 6, 2025

Can I use 16x25x4 instead of 16x25x1?

No, you cannot use a 16x25x1 filter instead of a 16x25x4 filter because the thickness is wrong, and it can cause issues like poor filtration, air leaks, and strain on your HVAC system. The 1-inch filter is too thin to fit securely, and the increased resistance from trying to fit multiple 1-inch filters can damage the unit. You should use the correct 4-inch filter for proper airflow and system performance.
 
Why you should not substitute:

• Poor fit: A 1-inch filter will not seal properly in a 4-inch slot, allowing unfiltered air and dust to bypass the filter. 
• Reduced filtration: The smaller filter will trap fewer particles and will clog faster, which is counterproductive to air quality. 
• System strain: A 1-inch filter will not provide enough surface area and can create too much resistance, forcing your HVAC system to work harder, which can cause damage and lead to higher energy bills. 
• Unnecessary resistance: Using multiple 1-inch filters to make up the thickness does not increase the surface area and will only increase airflow resistance, potentially damaging your system. 

What to do instead:

• Find the right filter: The best option is to find a 16x25x4 filter. It may be necessary to order it online or from a specialty supplier if your local store doesn't carry it. 
• Use a temporary adapter: If you absolutely must use a temporary solution, you can use a filter frame adapter to make the 1-inch filter fit properly, but it is not ideal for long-term use. 
• Consult a professional: If you cannot find the correct filter, it's best to consult an HVAC technician to ensure you don't damage your system. 

Which is better, PM 0.1 or 2.5 filter?

Bringing it back to filters, the PM0. 1 is capable of capturing smaller particles than the PM2. 5, which means it can capture more particles while still allowing you to breathe comfortably.