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What’s a Standard Air Filter Size?

November 14, 2018
Measuring for an Air Filter Size | Standard Air Filter Size Image

What are the Most Common Filter Sizes?

What are the most common HVAC filter, furnace filter, and ac filter sizes? Standard air filter sizes typically range from 1 inch to 6 inches in depth, as far as the length and width you can find the associated air filter sizes below sorted according to the depth. Complete list of the most common air filters: 

1" Air Filters: 10x30x1, 12x12x1, 12x20x1, 12x24x1, 12x30x1, 14x14x1, 14x18x1, 14x20x1, 14x24x1, 14x25x1, 14x30x1, 15x20x1, 16x16x1, 16x20x1, 16x24x1, 16x25x1, 16x30x1, 18x18x1, 18x20x1, 18x24x1, 18x30x1, 20x20x1, 20x22x1, 20x23x1, 20x24x1, 20x25x1, 20x30x1, 24x24x1, 24x30x1, 25x25x1

2" Air Filters: 16x25x2, 20x20x2, 20x25x2

3" Air Filters: 16x25x3

4" Air Filters: 16x20x4, 16x25x4, 20x20x4, 20x25x4

5" Air Filters: 16x25x5, 20x25x5

6" Air Filters: 20x25x6

   Get Started   

Air Filter Sizes for Your Home Can Be Frustrating

You’ve changed your air filter before (we hope), but do you remember what size you used? Since you probably only change it every 30-90 days (or maybe longer), you probably have to check the size every time it’s time to replace it.

Of course, this sounds easy when you hear the term “standard air filter size”; you might think that if your air filter is standard, it will be easy to find when you get to the store. Unfortunately, that’s not the case – there are about 20 “standard sizes” for air filters, and none have the same measurements.

Why is getting a correctly sized air filter so important? Because incorrectly sized (and incorrectly installed) air filters cause air seepage and decrease filter effectiveness. Even worse, incorrectly sized air filters can place undue stress on your HVAC system, damaging it and increasing your energy bills.

So how do you find the right air filter?

How To Measure Air Filters? Don't forget to Measure!

Follow these 3 easy steps to accurately measure your air filter size:

1. Measure the Length 

2. Measure the Width

3. Measure the Depth

=         L x W x D

Sometimes, the size is written on the air filter, in which case you can just head to the store or shop here and get the one that’s the same size.

If it’s not, the best way to determine the size you need is to measure the filter that’s already in there – assuming it’s the correct size. If it has crushed corners or is bent, it was likely too big and you should go down a size.

Standard Air Filter Sizes May Vary Slightly

Air filters aren’t meant to be snug. In fact, if you have to force an air filter in or out, it’s the wrong size, which is why standard sizes are often half an inch smaller than they’re advertised. This can be confusing because if you need a 16 x 25 filter, you’ll find it measures 15 1/2 x 24 1/2.


Take the Easy Road & Order Your Correct Air Filter Sizes With Us

OR you could try FilterTime. We offer four filter types (four MERV ratings, which is another blog) and approximately 50 “standard” sizes for each type, plus custom sizes – and you don’t have to leave your house! Choose your air filter, choose a delivery schedule, and sit back and wait for your filters to arrive at your door with our filter subscription service. 

Contact us to learn how to get the air filters you need when you need them.

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