What Are the Most Common Furnace Filter Sizes and Where to Buy Them?

When it comes to furnace filters, size matters. The right size filter is essential for keeping your HVAC system running smoothly and taking advantage of all the benefits your air filter has to offer. But what are the most common furnace filter sizes and where can you buy them? Let's take a look. Most domestic HVAC systems use a low MERV (1-) fiberglass filter with a nominal size of 1 inch thickness. This rounded measurement is called the nominal size and is used to match the correct filter to the air cleaner slot of the accessory.

The filters are labeled with three-part dimensions: the first number is its length, the second is its width, and the third is its depth or thickness. For example, one of the most popular furnace filter sizes is 20 x 25 x 1 inch, with an actual size of 19.5 x 24.25 x 0.75 inches. MERV stands for Minimum Efficiency Reporting Value and is not a brand or type of filter, but rather a scale for classifying air filters based on their particulate removal efficiencies. The image of this 12 x 12 x 1 inch air filter has the nominal size, which is the size that air filters are usually sold for. Homeowners should always use the right furnace filter sizes to protect the comfort of their home, indoor air quality, and reduce HVAC costs. Upgrading this AC filter to a medium efficiency filter (MERV 5-) can have a significant effect on improving the air quality in your home.

They are seven times better than a standard filter for removing dust and other particles and have a longer service life than other filters (up to two more years). Even though there are now filters that are also meant to protect air quality, the filter is located before the equipment to protect your system. Oven filter sizes with a thickness or depth of one inch generally need to be changed more frequently. If your filter doesn't have the actual dimensions on the outside of the filter, you can measure it to get the correct dimensions. As long as homeowners know how to read them and where to find them, they should have no problem replacing furnace filters at home.

Heating and air conditioning technicians can accurately assess home goals, indoor air quality and lifestyle to get the perfect furnace filter sizes.

Marla Cloonan
Marla Cloonan

Devoted web guru. Professional internet maven. Typical social media specialist. Wannabe social media lover. Certified food aficionado. Incurable bacon enthusiast.

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