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Why Picking the Right Filter Size Matters

Too Small? The air might sneak around the edges of the filter, causing noise and letting dust and other tiny bits float around your home.

Too Big? The filter will not fit into the vent/return.

Getting it Wrong? It could end up costing you more since sending back wrong-sized filters isn't cheap.

How to Avoid Mistakes

Know the Difference: Nominal vs. Actual Size

  • Nominal Size is the rounded number you see in ads or on boxes.
  • Actual Size is the real deal – the exact size of the filter.

Think of it like this: a filter might say 20x20x1 inches – that's the nominal size. But in reality (actual size), it might be a bit smaller - 19.5x19.5x0.75.

Both these sizes should be on your filter or heating/cooling system. Can't find them? Best to grab a tape measure and check. If you don’t have an existing filter to measure, simply measure your return vent.

Finding Your Filter on Our Site

  • Go to our homepage at
  • Pick the type of filter you need, like one for a furnace.
  • Choose the thickness (it's usually a number from 1 to 6 inches).
  • Next, pick the length and width (like 20x20 from our example).

Can't find your size? No worries, we can make one just for you. Just ask us!

Can't Find Your Size? Use the Model Number

Sometimes filters have a model number (like "Honeywell FC40R1094"). Just type this number into our search bar.

Checking Your Choice

Did you find a filter? Great! Just double-check that the actual size listed on our site matches your needs. If it's super close, you're good to go.

Still Unsure?

If you're still scratching your head about sizes, just give us a shout or send us an email. We're here to help make sure you get the right fit!