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How to Measure HVAC Air Filter Size

It is essential to use the exact size of HVAC air filters to keep the system running efficiently. The air will not get filtered if you are not aware much about HVAC filter sizes. So, choose the right air filter to maintain the furnace’s efficiency and keep the air of your house clean and refreshing.


Does The Size Of The HVAC Air Filter Matter?

Yes, it matters. Using the right size air filter for your HVAC system is an essential task for you. You can purchase a good HVAC filter that is perfect in size from some online sellers or HVAC service companies. You may find some reliable online retailers, like Custom Filters Direct, delivering top-quality air filters directly to your door. Don’t consider HVAC air filter sizes if you want to reap all its benefits.

What Is The Standard HVAC Filter Size?

While shopping for an air filter, you should remember that the air filtration industry supplies filters a bit smaller than their slot or frame. The reason is to get them to slide into places without getting bent. There are differences between the nominal and actual size of HVAC air filters.

  1. The Nominal Size: The nominal size usually depends on the frame. For example, The nominal size of an HVAC air filter can be 16× 25 × 1″.
  2. The Actual Size:  You will be able to see the actual size of an HVAC air filter in the fine print on the frame of the filter you bought. The actual size of the filter could be 0.25″-0.5″ smaller than the nominal size. Another criterion of the actual sized air filter is that the sizes depend on the brand. But you can hear from any residential air filter supplier that any standard size can suit a standard residential unit. An example is 15.5×24.5×0.75″ or 15.75×24.75×0.75″.

The first thing you must remember is what size HVAC air filter you have. It should fit into the slot properly; otherwise, you will not be able to prevent the dirty air from infiltrating inside the house. 

Measure Your HVAC Air Filter Size Following Few Steps

Sometimes, many consider that measuring the air filter sizes is tricky without getting help from experts. But, this is not a difficult task.To measure your HVAC filter size just by following a few steps-

  1. Examine The Frame Of The Filter: First, you should remove the existing filter from its place. Then, test the filter’s frame where the filter size is printed in bold form along the edge of the frame. The given size is the nominal size of the filter, which is different from the actual size. You should double-check if the actual dimensions are not listed on the filter’s frame. 
  2. Measure The Air Filter: In the next step, you should measure the air filter. You can use a ruler, inch tape, or any measuring device. Turn the AC off as a safety precaution. Before removing the furnace filter, turn off the AC handler. Measure the length, depth, and width of the filter. 
  3. Measure Air IntakeWhen You’re Suspicious About The Size: If you are in doubt about whether the size is suitable for your furnace or not, it is recommended to measure the air intake. Ensuring the correct sized filter is needed. 

Problems For Using The Wrong Size HVAC Air Filter

Though a wrong size air filter does not immediately damage the HVAC system, it reduces the efficiency of your house’s cooling and heating system. The issue becomes more apparent when it is time to pay the next utility bill. Another major issue of using the wrong filter is that it can’t prevent the dust from building up on the motor and blowers of the HVAC system. The dirty furnace can massively affect the performance of the filter.


When you are not sure about what air filter size will be good for you, you can make a call to an expert. Make sure you use the accurate size HVAC air filter to make the air quality of your house excellent.


Welcome to the Night Helper Blog. The Night Helper Blog was created in 2008. Since then we have been blessed to partner with many well-known Brands like Best Buy, Fisher Price, Toys "R" US., Hasbro, Disney, Teleflora, ClearCorrect, Radio Shack, VTech, KIA Motor, MAZDA and many other great brands. We have three awesome children, plus four adorable very active grandkids. From time to time they too are contributors to the Night Helper Blog. We enjoy reading, listening to music, entertaining, travel, movies, and of course blogging.

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