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How to Measure to Determine Your Air Filter Size?


How to Measure to Determine Your Air Filter Size?

With a wide variety of air filters available in different sizes, finding the right filter for your air conditioning unit can be a bit of a headache. There are literally thousands of air filter sizes.

So how do you determine the size of your air conditioner filter and purchase the correct size replacement air filter.

Check the air filter size on the side of the air filter
Most filters are marked with two size measurements, which can be found on the side of the filter. There is usually a "nominal" size written in a large font, and an adjacent "actual" size written in a smaller font.

Air Filter

This is the easiest and most obvious way to find the size of an AC filter, but not all filters list size measurements. In this case, finding the size of the filter required some manual measurements.

The Difference Between Nominal and Actual Sizes in Air Filter Measurements.

Many of our customers are sometimes confused by the difference between the nominal size listed on the replacement air filter and the actual size.

Nominal Air Filter Size - "Nominal" sizes list general sizes, usually rounded up or down to the nearest whole number or half, to make it easier to keep track of size dimensions for ordering replacements. This is a shorthand that defines the size of the vent that the air filter itself can fit comfortably.

Actual Air Filter Size – The actual size of the air filter is usually less than 0.25" - 0.5" and shows the actual size specification of the air filter.

Sizes listed in large print on filter sizes are usually "nominal" filter sizes. We do our best to specify actual sizes on our website to avoid confusion, however, filters within 0.25" or less of existing filters are generally interchangeable.

How to Measure Air Filter Size?
If the size isn't written on the side of the air filter, the next step is to get out your trusty measuring tape.

How to Measure to Determine Your Air Filter Size

You need to measure length, width and depth.

For air filters, the length and width dimensions are interchangeable, although usually the larger dimension is width and the smaller dimension is length. The smallest dimension is almost always depth.

For example, if the air filter measures 12" X 20" X 1", it would look like this:

Width = 12"
Length = 20"
Depth = 1"

In some cases the length and width can be interchanged, but you always need to be sure to measure these 3 specific air filter or furnace filter sizes.

Below you can see an example of an air filter size chart:

Air Filter1

As for depth measurements, standard air filter sizes are nominally 1" (0.75" actual), 2" (1.75" actual), and 4" (3.75" actual) deep. These standard air filter sizes are easier to find and are the most commonly used. To shop these standard filters by size, click below.

What if the standard filter size doesn't match your air filter size?
Custom AC or furnace filters allow you to choose a custom size if the standard size doesn't work for you.

Whether you decide on custom or standard, we always offer the ability to choose filter performance grades, choose filter quantities, and choose whether you want your filters delivered on a regular basis.

Air Filter2

If the filter you're looking for doesn't fit into these standard sizes, you can offer a matching brand or request a custom sized filter!

Post time: Feb-22-2023