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How to Measure Your Air Filter

By May 28, 2019November 29th, 2020No Comments

A common question that we see is “How do I figure out what size air filter I need?”

Whether you recently moved into a new home or a lot of time has passed since you last changed your air filter, we’ve put together a guide to show you how to measure your air filter.

First thing you need to know is that there are 2 types of measurements for air filters:

  • Actual
  • Nominal

Here’s a quick video to explain the difference:

Still confused? Nominal measurements will look like this 12x30x1 while an actual measurement will look like this 11.75” x 29.75” x 0.75”.

In many cases, you will find most air filters sold online and in stores are sold by nominal measurements and not actual measurements.

More than likely, you will probably not have to measure to see what size air filter you need. Why? Because many air filters (including brand air filters) have the measurement printed on the sides of the air filter. Locate that number on your existing filter and you’re all set!

Now that you know what size filter you need, you’ll need to pick a MERV that matches your filtration priorities. Don’t know what a MERV you need? Check out this blog post.

Now that you know what size air filter you need and what MERV rating best fits your filtration needs, you might be asking, “How often do I need to change my air filter?”.

While how often you change your air filter is ultimately up to you, we suggest changing your air filter every 1-3 months. It is a good idea to periodically check the state of your air filter because a dirty air filter will not only harm your health it can also wear out your system.

Now that you’ve learned what you need to know about your home’s air filter, would you like to forget it? With the Home Filter Club, you can create a subscription for your air filters and have them delivered when you need replenishing! We’ll remember what size and MERV rating you need, and send them to you at the frequency you select! How cool is that?! For more information about our Home Filter Club subscription, click here.

Did we miss something? Let us know in the comments below!


This blog post is approved by the National Air Filtration Association (NAFA) because it aligns with their mission to educate end-users about the importance of air filtration. To learn more about NAFA, click here. is a replacement water and air filter company located in the United States. The views and opinions contained herein are solely those of the original author and do not represent Eco Blue Life or its affiliates. This article was originally published on  
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