Air Filter Size Chart: Choose The Right One

Although the air filter may seem like a small device, it is used to provide clean air from the air conditioner. Failure to install the correct air filter will result in damage to equipment, including respiratory problems. That’s why following the correct air filter size chart is important. 

Since I’ve experience with air filters, I’ll share everything here. This is an attempt to avoid any inconvenience while installing air filters. Hopefully, after reading this article, you’ll have no more questions about this. So stay with me throughout the article to learn about air filtering.

I’ve attached a complete chart about the size of air filters. Moreover, you’ll learn about the dangers of using the wrong air filter. So let’s get started. 

Air Filter Size Chart: Choose The Perfect One

The size of an object is typically measured by its length, width, and depth. But in order to determine the exact size of the air filter, the measurement of the long direction is taken to be the width. The shortest aspect is the length, and the smallest dimension is the depth or thickness. Follow the chart below to choose the air filter. 

Standard Air Filter Sizes(Inches)

How To Choose A Right Size Air Filter System? (3 Things To Consider)

Such questions don’t have a straight answer, and the reason is there are a few factors that determine the whole thing. When you think about the proper air filtration size, you’ll also need to consider factors such as CFM and RPM rating. 

Clearly, without getting involved in these factors’ discussion, you cannot decide the proper size. So, I will surely include some factor chat and then tell you what the proper size should be like. Keep on Reading.

1. Size Based On CFM

The first thing you need to know is that the shop air filtration system must clean air inside your house or workshop six to eight times per hour. And this means the entire volume of air inside that area needs to pass through the filtration system at least six times in one hour.

The area covering speed of an air filter system is measured with a CFM unit. It means cubic feet per minute. And refers to how many cubic feet of the area the air filtration system can clean each minute. With more CFM, you get more filtering coverage.

Usually, residential houses and small garages do not need to go more than 400 CFM. The information of CFM should be in the product description segment. The air volume is measured through CFM, and you need to match this with the system’s CFM. To do so, you need to calculate the volume of your workshop. Basically, you need that area’s height, width, and length.

And then multiply all three to get a figure. Then multiply the figure with the total number of times you want the air to be cleaned. Probably 6 to 8. Finally, divide your achieved figure by 60.

For example, imagine you have a workshop with an 8 feet ceiling, while the other measurements are 25 x 15 feet. You’ll find the volume of that workshop to be 3000 cubic feet exactly. Suppose you want the filtration system to work 7 times each hour. So, you’ll have to multiply 3000 with 7 and get 21000. Now divide it by 60 to get 350 CFM. And this means the ideal size of your air filtration system should be something capable of 350 CFM.

2. Size Based on Motor

For a small or medium-sized workshop, the size of an air filtration system also means the power of the motor it comes with. And so, this measurement is undoubtedly going to come into play. First, don’t go for anything less than 1/3 HP for a small workshop. And if it’s a medium size shop, then a filtration system with a 1/5 HP motor size should work best.

RPM is also an important factor that relates to the motor. It’s actually the short form to revolutions per minute. And this refers to the motor spinning blower fan or wheel speed. It works to suck all the pollution out of the air. And that’s why RPM is a huge factor you can’t miss for picking proper size filtration for your shop.

Go for air filtration systems that come with ranges of RPM. Usually, you get to choose from 1700, 1400, and 1200 RPM. You adjust the airflow speed according to your convenience.

3. Size Based On Dimension

Air filters have diverse diameter ranges. Hunger is better; it will usually fit in bigger rooms. However, the shape can make things somewhat different. Some models are quite wide but at the same time short too. Also, you’ll see options with a tall body that is thin too. Usually, the depth is somewhere between 10 to 20 inches.

The whole shape and size matter deeply relates to CFM and RPM rating. That’s why you should be considering not just the actual dimension of a system but its other calculative figures.

However, for a small garage with less space, you should route for something not too large. Or elsewhere will you place it? And if the space inside is pretty huge, then go ahead and get a bigger one that can give better area coverage.

What Happens If You Put In The Wrong Size Air Filter? 

Air filters control the airflow in your home. Buying the right air filter is therefore essential. Otherwise, it will interfere with the whole process of your air circulation. Below I have listed some incidents that actually can happen if someone doesn’t install the right air filter.

  • The Space Won’t Adjust Properly

Air filter should be adjusted properly throughout the space. The too-large filter won’t fit properly in the slot. Similarly, the whole space may not be covered with a tiny air filter. As a result, dust, fur, and pollen will enter easily.

  • Poor Air Quality

Air filters come with different MERV (minimum efficiency reporting value) ratings. The higher the MERV rating, the finer the air filter. Therefore, air filters with higher ratings should not be used more than they were designed for. Because the HVAC system may not have that amount of power. Otherwise, air can’t flow properly. 

  • Energy Bill Rising

The wrong air filter has a great effect on the performance of the HVAC. If your filter is thicker, it needs to expend more energy to prevent polluted air. This will increase the cost of cooling and heating. So choose the right filter to improve your comfort and health.

  • Frequent HVAC System Repairs

Improper air filters don’t provide enough airflow to electrical power devices. It can lead to a breakdown of the entire system. This will require you to repair the HVAC system frequently. The wrong air filter will fail to operate the system efficiently.

5 Things To Consider For Choosing The Perfect Air Filter Size

Choosing the perfect air filter size is crucial for maintaining the optimum level of air quality. There are several things to consider when determining the right air filter. Keep in mind these things for choosing the perfect air filter size. 

1. Dimensions Of The Air Filter

The first and main consideration is to know the dimensions and then choose the right air filter. Ideally, you should know the system’s size, but if you don’t, you can calculate it manually.

Take note of the size of the cooling unit and filter. Recorded the dimensions of length, width, height, or thickness well. All measures will be in inches.

2. The Type Of Air Filter

On the market, you will find many types of air filters, such as HEPA filters, electrostatic filters, carbon filters, electronic filters, and many more. There are various models under these.

In the case of allergies, choose an electrostatic filter or a HEPA filter. These are effective in removing microscopic allergens. A carbon air filter is better for more ventilation.

3. Consider Thickness

Thickness plays a significant role in the durability of an air filter. For example, a 1-inch thick fiberglass filter must be changed every 1 month. But a 4-inch-thick filter is usually 6 to 12 months durable. It also works quite well for large spaces. 

4. The Material

An important aspect to consider is the components of the air filter. You’ll find different filters, such as polyester, cotton, and fiberglass. Fiberglass is a reliable resource in preventing contaminants. It is very effective in preventing pet dust and pet dandruff.

5. Consider The MERV Rating

You need to pay attention to the MERV rating of the air filter. A higher MERV rating indicates a better air filter. But a higher MERV rating will require more energy to pass through the air. Thus, stronger systems are necessary for higher MERV ratings.

A higher MERV rating air filter can filter up to about 0.3-1 microns. Notice the chart below.

MERV RatingGroup 3(3-10 microns)Group 2(1-3 microns)Group 1(0.3-1 micron)

Related Questions About The Air Filter Size Chart

How Do You Know What Size Air Filter You Need?

You can easily find out its size by checking the old air filter. The size of the filter is usually printed with the frame. As might be “10x20x1”, where 10 is length, 20 in width, and 1 is thickness.

For some reason, you may not get the printed measurements on the old air filter. Then measure the length, width, and thickness with tape. If the first two methods fail, measure the air filter’s slot. Remember, the measurement of the filter slot will be the actual size.

What Are The Standard Air Filter Sizes?

The thickness of standard air filters is usually 1 inch, 2 inches, or 4 inches. Standard air filters are usually cut nominally, with values ​​up to 1/2 inch undercut. For example, the actual size of a 12 X 24 filter is 11-1 / 2 X 23-1 / 2. However, at the time of air filter replacement, check the existing filter in the air conditioner. 

A new filter should be set according to that measure if it is well attached. Additionally, check whether it has been forced to fit into the system. However, make sure that the standard filters have a steel frame.

Do Air Filters Have To Be An Exact Size?

You must know the exact size of the air filter. During packaging, the nominal size of the air filter is printed. In addition, this is a circular number that introduces the filter. So you need to know the exact size of the air filter. This is the actual measurement of your filter.

The actual measurement may also include a fraction of a number. Such a “10x10x1” measurement is nominal. Its exact size is “9.5 x 9.5 x 0.75”.

Can You Cut Down Air Filters To Fit?

You can cut down the air filter to fit the slot. But for this, you need to have experience. Incorrect cutting can cause the filter to lose its integrity. Also, follow the manufacturer’s instructions. Check whether the air filter is cuttable. 

Follow the manufacturer’s instructions for filters that allow you to cut them. Otherwise, better to refrain. If you can cut it properly, it will not weaken the filter.

Is It Ok To Use A Smaller Air Filter?

It is not ideal to use a smaller air filter. A small air filter is not recommended because so often it does not work properly. If you use a small-sized air filter, the indoor air quality will not improve. This small filter allows mold, dust, and other contaminants to enter.

In other words, you won’t get the benefits of an air filter when using a smaller one. So, choose the perfect filter. Buy a filter that will fit snugly by measuring the filter slot.

Are Thicker Air Filters Better?

Thicker air filters capture more air particles. Experience has also shown that thicker air filters are more durable and do not need to be replaced at short intervals. For example, a 1-inch fiberglass filter must be replaced every month. But if you use a 4-inch thick filter, it can last 6 to 12 months. 

So you can say that thicker air filters are better than thin ones. Generally, most filters are 1 inch thick. In some cases, the thickness can be up to 5 inches.

Final Verdict:

Regular air filter replacement is important to manage your filtering system efficiently. This will make your home a healthier environment by reducing pet fur, pollen, dust, and allergens. Hence, follow the air filter size chart to select the correct one.

The presence of furry pets in the home can significantly impact air filters. Air filters should be changed every three months to ensure proper performance. And don’t forget to check it every month.


RESIDEO NEWSROOM. (2020, May 22). Resideo Pro | Professional Support For Contractors & Experts. Resideo.

What is a MERV rating? | US EPA. (n.d.). US Environmental Protection Agency. Retrieved July 3, 2022, from

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