How to Measure Your Air Filter

What Size Home Air Filter do I Need?

Odds are if you found yourself reading this article, that probably means that it’s time for your first filter change! There are a lot of things to consider before you pick a filter, but the most important factor to know is what size filter do I need. The good news is that determining your size is a one-time job, and we are here to make it easy!

Understanding You Filter Dimensions

There are three measurements to consider when measuring a filter: Length, Height, and Width. On all filters, you’ll find three numbers (ex. 20x25x1), this can be read as height by length by width. In the United States these measurements will always be done in Inches.

*It is important to note that many companies will often round their measurements to the nearest inch, for example AirThreds filters actually measure .25 inches shorter than the listed sizes

**If there is only two measurements, assume the width is 1 inch

How to Measure for Your Filter

It is extremely rare that you’ll find your HVAC unit without a filter in it, but if that happens to be the case you should contact your home’s developer or a HVAC professional so they may inform you on what type and size filter will work best for your specific unit. Now let’s go over what to do if you do have a used filter.

Before you break out the tape measure, first check the side of your filter; oftentimes, companies will list the size on the side of their filters in the format shown above. If no size is listed, simply measure each of the three dimensions, making sure that your measuring device is parallel to the side which you are measuring.


Remembering Your Filter Size

Earlier I told you that measuring your filter is a “one-time job”, but that’s only true if you can remember the size of your filter.

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