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Standard Stock Size Air Filters

Facts About Standard Sized Air FiltersHave you heard the term "Standard stock size" air filter? This merely means that your HVAC unit has a filter that is a common size that is mass produced and easily found. For example: 16x20x1, 20x20x1, 16x25x1, 20x20x1 are all standard sized air filters. Every unit has a specific sized filter which allows it to perform correctly and efficiently. Most AC and HVAC units use standard sized filters, but some do require a custom size air filter to be purchased and installed. But why is filter size important? According to, incorrectly sized or installed filter frames can cause air seepage, which significantly decreases filter effectiveness. Also, if there is any air flow resistance caused by using a filter that is not correctly sized, it can result in unnecessary stress on the HVAC unit itself, potentially damaging your system equipment and increasing your energy bills.

Standard Size Air Filter Facts

  1. There are only about 10 of the most common air filter sizes available at retail locations. US Home Filter makes over 80 standard stock sizes that local stores do not have the shelf space for, nor the inventory capacity to keep them in stock. We do manufacture and stock them all because that's our business! So take a look at our stock filters, from the most common 16x20x1, 20x20x1, 16x25x1, 20x25x1 to other sizes like 8x16x1 to 30x36x2 to 25x29x4 to 20x25x6. If we don't have it, we can make it!
  2. Nominal Size: This is the approximate size, such as 16x25x1. All 16x25x1 filters are designed to fit standard 16x25x1 filter slots.
  3. Exact Size: This can vary slightly depending on the manufacturer. The die-cuts (filter frames) are manufactured in bulk and purchased as a raw material for making air filters and determine the exact size of the air filters. The exact size is always slightly smaller than the nominal size to allow the filter to properly fit in the slot or housing. For example, a stock size of 20x20x1 may have exact dimensions of 19-1/2 x 19-1/2 x 3/4. This is completely normal and is the standard in air filter manufacturing.
  4. Slight variances in size may make a difference in certain situations. For instance, you may find that the stock size at your local hardware store is just a bit too big to fit your housing slot; however, you may be able to find the same stock size online by a different manufacturer that is slightly smaller size and it fits perfectly.
  5. There are thousands upon thousands of possible exact air filter sizes that can be used in an HVAC unit. Because of this, you will not always be able to find a filter at a store or online as you are able to find regular stock sizes. If this is your situation, you will need to order a custom size air filter. Custom filters are not made to a nominal size, with a smaller actual size as stock sizes are made. At US Home Filter, we make your custom size filter according to your HVAC manufacturers' specifications.

Finding the Right Fit

The filters don’t need to fit with an “airtight” seal, but you should be able to easily install and uninstall your filter without a struggle. Your filter should be a bit smaller on each side of the filter housing slot, allowing you to slide the filter in and out with ease. For most systems you can use a standard sized filter within 5/8 of an inch smaller than the air filter housing.

US Home Filter is Here for YOU

Hopefully this information helps you better understand what your AC/HVAC system requires for optimum performance. It's also important to remember that using the correct size filter for your system protects your AC/HVAC unit from malfunctions and damage, allowing it to continue to perform correctly and keep your air cleaner and your family and home safer. Take a look at our air filter measuring guide for steps on figuring out the correct size filter for your system. If you're still unsure, US Home Filter is here to help! Call us at 855-237-1673 or contact us online.

Order now from US Home Filter and receive FREE SHIPPING on your order!

Selecting the filters that are just right for your home can be difficult and confusing at times. At US Home Filter we understand this, which is why we offer an experienced staff to help answer any questions you may have. For personal assistance with your air filter needs, please contact us now online or call us at (855) 237-1673 and we will do our very best to assist you in selecting the right filter for your individual needs. We want to earn your business and we guarantee your satisfaction! Take advantage of our quality products, vast selection, low prices, and enjoy FREE SHIPPING on every air filter order within the Contiguous USA.

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