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The sizes below are plus or minus 1/8". The Nominal size is but just a name. This is why you will see, for instance. three 20x25x5 and all three will have different "Actual" sizes. This is because 20x25x5 is just the name of the filter and the actual size depends on the manufacturer.

Many manufacturers use the same sizes so when you click "Go TO IT" you may land on a page that has your size but a different brand than what you have. This is OK because these are aftermarket filters and the only thing that matters is the actual size of the filter.

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12x20x4 1/4 ( 12 1/8" x 19 7/8" x 4 1/4" ) GO TO IT
16x20x4 1/4 ( 15 1/2" x 19 7/8" x 4 1/4" ) GO TO IT
16x20x4 ( 15 7/8" x 19 3/4" x 4 3/8" ) GO TO IT
16x21x5 ( 16 1/4" x 21" x 5" ) GO TO IT
16x22x5 ( 15 3/8" x 21 7/8" x5 1/4" ) GO TO IT
19x20x4 1/4 ( 19 1/8" x 19 7/8" x 4 1/4" ) GO TO IT
16x25x3 ( 15 3/4" x 24 1/4" x 3" ) GO TO IT
16X25X4 ( 15 7/8" x 24 3/4" x 4 3/8" ) Honeywell & others GO TO IT
16X25X5 ( 15 7/8" x 24 3/4" x 4 3/8" ) Carrier GO TO IT
16x25x5 ( 15 3/4" x 24 1/4" x 4 3/4" ) GO TO IT
16x25x5 ( 15 3/8" x 25 1/2" x 5 1/4" ) GO TO IT
16x26x5 ( 16 1/8" x 25 3/4" x 4 7/8" ) GO TO IT
16x28x6 ( 15 3/8" x 26 15/16" x 6" ) GO TO IT
20x20x4 or x5 ( 19 3/4" x 20" x 4 3/8" ) GO TO IT
20x20x5 ( 19 3/4" x 20 5/8" x 4 7/8" ) GO TO IT
20x20x5 ( 20 1/4" x 20 3/4" x 5 1/4" ) GO TO IT
20x21x5 ( 20 3/4" x 20 5/8" x 5" ) GO TO IT
20x22x5 ( 19 9/16" x 22 " x 5 1/4" ) GO TO IT
20x23x4 1/4 ( 19 7/8" x 22 5/8" x 4 1/4" ) GO TO IT
22x24x5 ( 22 1/8" x 24 " x 5 1/4" ) GO TO IT
20x25x4 or x5 ( 19 7/8 x 24 3/4 x 4 3/8 ) Honeywell & others GO TO IT
20x25x5 ( 19 7/8 x 24 3/4 x 4 3/8 ) Carrier GO TO IT
20x25x5 ( 19 5/8" x 24 3/8" x 4 3/4" ) GO TO IT
20x25x5 ( 20 1/4" x 25 3/8" x 5 1/4" ) GO TO IT
20x25x6 ( 19 3/4" x 24 1/4" x 6 3/8" ) GO TO IT
20x26x5 ( 20" x 25 7/8" x 4 7/8" ) GO TO IT
24x25x5 ( 23 3/4" x 24 3/4" x 4 3/8" ) GO TO IT

Sizes from the table above will be for brands such as: Air Bear Filters, Airguard Air Filters, Amana Air Filters, American Standard, Aprilaire Air Filters, Armstrong Air Filters, BDP Air Filters, Bryant Air Filters, Carrier Air Filters, Coleman Air Filters, Comfort Plus Filters, Day and Night Air Filters, Electro Air Filters, Emerson Air Filters, Five Seasons Air Filters, General Air Filters, Glasfloss Air Filters, Goodman Air Filters, Honeywell Air Filters, Lennox Air Filters, Maytag Air Filters, Payne Air Filters, Purolator Air Filters, Skuttle Air Filters, Space-gard Air Filters, Totaline Air Filters, Trane Air Filters, Ultravation Air Filters, White Rodgers Air Filters,

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20x25x5 air filter display
By the time you finish reading this article you will learn
the sizes you see on these filters are not the true, real size
20x25x5 air filter sizes

20 x 25 x 5 Air Filter
NOMINAL FILTER SIZE VS. ACTUAL FILTER SIZE has created a very good website but mistakes can be made when ordering because air filter sizes are confusing. Correction: Air filter sizes are insane!

A customer ordering a 20" x 25" x 5" air filter can easily order the wrong size through no fault of their own. Ordering the wrong size creates a real bad problem for the customer because, "It can cost a King's ransom to return these big air filters."

Let me explain. In the air filter world, filters are labeled by "Nominal" sizes and Actual" sizes. A 20" x 25" x 5" Nominal (by name only) air filter will have a different "Actual" size. The nominal size is written on the filter frame so the customer will order a 20" x 25" x 5" not realizing there are many 20" x 25" x 5" air filters, and that they all have different actual sizes depending on the brand of the filter.

Now this customer may have a problem because these 20" x 25" x 5" filters are not interchangeable, so if the filter this customer ordered has the wrong "Actual" size, the air filter will not fit the filter cabinet or filter housing. Of course he might get lucky and end up with a filter that has the correct actual size....ring...ring...ring...We have a winner!

In case you are interested, I have been in the air filter industry for 44 years. Yep, I'm really, really old! But don't despair, I still know what I'm talking about. What I don't know is why manufacturers confuse us with nominal sizes. I just spent over an hour for this article looking all over the internet in search of a reason manufacturers use nominal sizes instead of actual sizes. I should be so lucky.

I did find one site that wrote that the nominal size or the dimensions you see written on the frame represents the size of the space the filter fits into. Therefore, the actual size of the filter has to be a smaller size so that the filter will fit into that space.

Sounds good, at first, except there is a very popular 20 x 25 x 5 filter that is actually 20 1/4 x 25 3/8 x 5 1/4. As you can see, the actual size is bigger than the nominal size. There is another popular brand filter whose actual size is 19 3/4 x 24 1/4 x 4 3/4. In this case (20x25x5 filter) the air would flow right through the 24 1/4 side, unfiltered.

Now, having made a case for, "the manufacturers are trying to confuse us" theory, I have to give the website that wrote the nominal size is the size of the space the filter goes into, some credit. The reason being that what they wrote may be partially correct. In the case of standard pleated filters the actual size is consistently 1/2" smaller than the space it fits into. But wait! You have to be careful because some times the nominal size is actually the true size of the filter.

However, again in case you are interested, in my search of the web I found out why nominal sizes are used in lumber. The 2" x 4" nominal size board is actually 1 1/2" x 3 1/2". The board is called a 2 x 4 because this is the size of the board before it is dried in a kiln and planed. In this case there's a good reason for the nominal size.

I have created a table below to show you some of the actual sizes of a 20 x 25 x 5 nominal size air filter. On the website you might see a variation of 1/8 inch. You may disregard this 1/8 because it has to do with the way different manufacturers list their filters.


20x25x519 3/4 x 24 1/4 x 4 3/4

Carrier, Air Bear, Skuttle, Lennox, Airguard, Glasfloss, Others
20x25x519 7/8 x 24 7/8 x 4 3/8

Carrier, Honeywell, Amana, Airguard, Lennox, Glasfloss, Others
20x25x520 1/4 x 25 3/8 x 5 1/4

Carrier, Amana, Electro-Air, Goodman, Five Seasons, Others
20x25x519 3/4 x 24 3/4 x 3

Honeywell Grill Filter (Brand Name) - Has a Lip
20x25x519 7/8 x 24 7/8 x 4 3/8

Honeywell Grill Filter (AfterMarket) - Has a Lip
20x25x519 1/2 x 24 1/2 x 3 3/4

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Today so many people are using mobile phones to search for products and for educational information online. Mobile phones are such a great invention. Mobile phones have made life a lot easier and at the same time a more difficult. Easier because with a mobile phone we can search for products, like air filters and compare with online stores while driving our car or motorcycle (no, no, just kidding), but no, while walking through a department store or visiting a friend. And they make our life more difficult because we are constantly getting messages from friends, ads, and other notifications. It can drive you bunkers.

For shopping online mobile devices are great, even while you are sitting at home watching television you can search for your 20 x 25 x 5 air filter and order it right there on the spot. Next time you are out shopping or whatever and you remember you need to replace your air filter, use your mobile device and text us at 561-899-9266, or simply place an order right on your cell phone, smart phone, or mobile device.

So, How long do deep pleat, 4" and 5" filters last? This is a good question and an important one. But, a better question is, how often should the filter be changed.

These filters are deep pleat filters so they last longer than one inch or two deep air filters because they have have much more filtering area. There are many "rules of thumb" out there on how long these filters last with the most popular being six months. But, the truth of the matter is it really depends on how often you run your system and how dusty your neighborhood is. Still, that's hard to know, so my recommendation is go with the six months rule. But, I hasten to add, your blinkers will ultimately tell the story.