20x20x1 air filter actual size?

This is the standard in the manufacture of air filters. A 20x20x1 air filter actually measures 19-¾ x 19-¾ x ¾. This is what is known as undercut. All filters 1 and 2 are trimmed by a quarter of an inch to provide a little leeway and ensure it fits into the air return without being too big.

This includes custom sizes, so a 27-3/8 x 23-5/8 x 2 (which is the strangest size we can think of) is actually 27-1/8 x 23-3/8 x 1-¾. If you live in an older house, with a non-standard size air return frame, you can use adhesive foam insulation tape to slightly increase the dimensions of your preferred filter or order a custom-sized air filter. This means that in 1 and 2 air filters, the nominal size does not include the bottom cut and the actual size does include the bottom cut. The fact that the filter pleats run horizontally or vertically will not affect the effectiveness of your filter, so the number of unique air filter sizes on the market can be cut in half by always listing the smallest measurement first instead of having a 20x30 and a 30x20 as two completely different products.

If you measure your ventilation and find that you need a filter with a nominal size of 30x20, you will soon discover that there is no such thing as a 30x20. It's best to have some wiggle room in the slot of the HVAC unit, so you can easily slide the filter in and out without it bending or breaking. The actual size, as you might have guessed, is the actual dimensions of the filter by length, width and thickness. You also don't want to place an air filter 1 in a slot of 2 because the air takes the path of least resistance and will flow around the filter rather than through it if it's not the correct size.

Forcing an incorrect filter size on a filter can cause it to bend, damage the filter, or reduce its ability to function properly. Different manufacturers cut their whole house filters into different sizes and then round them to standardized measurements, meaning that two 20x25x5 whole house filters made by two different manufacturers are probably not the same size. For example, Home Depot mainly carries Honeywell brand air filters, while ace hardware mainly carries Filtrete. Then, use a measuring tape or other measuring device to measure the length, width and depth of the inner edge of the groove or frame of the air cleaner.

If the filter is not the correct size, whether it is too small or too large, air will flow around the filter rather than through it, and as a result, all the air will not be filtered out. If in doubt, you can always measure the air filter yourself with a ruler or any other measuring device. If you can't find your size in the store or need a custom-made air filter, online retailers are probably the best option for you. Most major retailers, such as Walmart, Target and Home Depot, carry air filters, albeit with a variety of different options and brands to choose from.

Robert Smisek
Robert Smisek

Total twitter nerd. Typical food trailblazer. Avid food practitioner. Unapologetic web junkie. Freelance twitter evangelist. Passionate food advocate.

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