When it comes to finding the right size air filter for your home, it can be a daunting task. But with a few simple steps, you can easily determine the size of the filter you need. Typically, the filter size is printed along the edge of the filter frame. Note that the size shown in bold type on the filter frame is the nominal size of the filter, which is likely to differ from its actual size.
To find out what size air filter you need, start by measuring the length and width (L x W) of your existing filter. If the filter is not square, the smallest measurement goes first. You can ignore the actual size printed on the filter for this task, since the nominal size is the set of numbers needed to order new filters. We recommend removing the existing filter and measuring it to confirm the actual dimensions.
This is important because if the filter were exactly the same size as the slot it fits in, it would be very difficult to install and remove it. Once you know the size of your old air filter, you can easily buy a new one with the same dimensions. If you buy a filter that's too large, it won't fit into the filter slot and you won't be able to replace the cover. When buying air filters, you will see both “nominal size” and “actual size” listed together.
It's important to remember that filters should be changed every 30 to 90 days, depending on their type and efficiency. If an air filter is too small, this will create air gaps and contaminants will avoid filter material. As for depth measurement, standard air filters are nominally 1 (0.75 real), 2 (1.75 real) and 4 (3.75 real) deep. In summary, when taking measurements of an air filter, you just need to round up to the nearest inch to find out what size air filter you need to buy. With this information in hand, you'll be able to purchase a new air filter with confidence.