If your current filter does not fit properly, or you do not have an existing air filter in your system, you will have to measure the grill opening or the filter slot of your air handler.

Because our air filters feature a Patented Anti-Bypass Seal, the filter does not have to fit edge to edge tight. As long as your measurement is larger then the inner lip of the grill, your filter will seal properly. Leave yourself room to remove and re-install it easily.


Q. How do I measure what size air filter I require?

A. Check to see if your A/C has an existing air filter in it. If so, does it fit properly? If it contains a disposable filter, are there any crushed corners or has the filter been forced into the system to fit? If not, measure the existing filter with a tape measure. That is the replacement size you should be ordering your new Custom Fit air filter.


Many air filter grills have obstructions such as stop tabs, rivets and screws. You want to make sure you take your measurement from in between these objects and subtract 3/8 inch, so the air filter will fit between them when you put it in.


Always open the air filter grill to take the measurement, don't assume the inside measurement is the same as the outside ac filter return air grill

High resolution clean residential air filter with metal mesh screen

If you have a filter already. Don't go by a size that is written or printed on the filter, it may be different then the actual size of the filter. Measure it.

Measurement Conversion Table (if you need to use it)

The rule of thumb is to measure from side to side and remove 1/8th of an inch to ensure your new filter frame fits properly without being too snug.

If you used a calculator and got a decimal, here's the conversion

.25 1/4
.375 3/8
.50 1/2
.625 5/8
.75 3/4
.875 7/8
Custom fit filter refills

It's worth it!

Taking the time to measure means you won't have to be bothered with it ever again. The frame is permanent, the refills are disposable.

When you order filter refills, we'll cut them to fit in your frame and ship them to your door.

Still Need help?

If you're still having trouble with the measurements or have any questions, we are here to help!

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