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How do I know what size air filter I need?

To determine the correct size of your air filter, you can check for the air filter dimensions typically labeled on the side of the filter. Look for two size measurements: a ‘nominal’ size, often in larger print, and an ‘actual’ size, usually in smaller print. It’s crucial to get the right size filter for your HVAC system’s health. A filter that doesn’t fit properly won’t effectively capture airborne particles. If the filter is too small, it will leave gaps for debris to enter, while one that’s too large won’t fit into the slot. Trimming it down isn’t recommended, as it can create gaps allowing contaminants to bypass filtration. Alternatively, you can examine your existing air filter, measure it yourself, or measure the air register or air filter slot to ensure the correct size.