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What Size HVAC Filter Do I Need?


The correct HVAC air filter is essential to keep an entire system running efficiently. The size of the air filter can be too small or too big. In both cases, you will face severe problems, and the air will not get filtered. Before you mess up with anything, take help from others when you feel the need. Be careful about using an HVAC air filter correctly to avoid the wastage of money and adverse air quality issues.

Ways to Measure an HVAC Filter

Measuring the HVAC filter of your house is an easy task that will cost little time and money. Without consulting an expert, you can measure an HVAC filter on your own. The following few steps, as given below, can help you to measure the HVAC filter without taking any help from an expert:

Examine the filter’s frame: Remove the old filter from its place. You notice what is printed in bold form along the edge of the frame. The nominal size given there is different from the actual size. Check out whether the actual dimensions are listed there or not.

Measure the air filter: The following step is to measure the air filter you will install. Use a ruler, inch tape, or any kind of measuring device. Before removing the existing filter, you need to turn off the AC handler. Take the measurements of the filter’s length, width, and depth.   

Are you suspicious about the size? Measure the air intake: You might be doubtful about the size of the air filter you want to replace with the old one. When you are unsure what HVAC filter sizes will be good for you, measure the air intake. 

Most Common HVAC Air FiltersSizes

An HVAC air filter is an essential component of a house to keep the house temperature comfortable and fresh. Understanding what air filter sizes apply to what types of places are essential. Get some knowledge about what filter size you need for your house. 

Currentlythe most common air filter size is 10×20, and this size is considered standard. If your system needs custom filters directly, note that many residential air filter suppliers can provide you with accurately sized HVAC air filters, such as Custom Filters Direct.

What Size Filter Is Helpful forMe?

Go over some different methods to help you determine what air filter size goes in your furnace perfectly. Before changing the furnace filter, you must consider the size of the new filter you will replace with the previous one. The new one should fit into the slot properly. Otherwise, the filter will cause the dirty air to infiltrate inside the furnace. Before replacing or changing the existing HVAC air filter, make sure you follow the three different methods are listed below:

  • Checking the old HVAC filter for its size.
  • Measure different dimensions of the old air filter.
  • Measure the air filter slot.

What Happens if the HVAC Filter Size Is Not Standard? 

We want you not to be one of those people who install improper-sized filters and, unfortunately, suffer from various problems. An improperly sized air filter causes poor indoor air quality and leads your HVAC system to struggle more than it should. Apart from these, it can also release a considerable amount of air contaminants without filtering out.

You will hear a rattling sound if the size is too small. The small air filter will make your house more dirty than usual. And then, if the air filter is too large, you will notice bent corners on the filter while removing it. These are some of the signs that should be noticed. If you alone can’t determine all these things, contact an expert to choose the right sized air filter for your furnace.


If you are a house owner and have an HVAC system installed, you must be aware of the negative consequences of not choosing the right size air filter. If you are satisfied with the performance of your old filter, you can choose the new filter from the same brand.

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