inside clean fresh air

How

How to Find Your Air Filter
And the Right Size

Finding your air filter is easier than it sounds.

Most homes have one main filter, and it's almost always in one of a few common places. You don't need tools, experience, or technical knowledge — just a few minutes.

1

Find Your Air Filter

Start with these locations (in order of likelihood):

Behind a Return Air Vent

  • This is the most common location.
  • Look for a large vent on a wall or ceiling
  • Often in a hallway, living room, or main area
  • The filter sits directly behind the vent cover
  • If the vent is bigger than others in your home, that's usually the return

Inside the HVAC Unit (Furnace or Air Handler)

If you don't see a filter behind a vent, check near your system.

Common spots:

  • Garage
  • Closet
  • Attic
  • Laundry room
  • Basement (less common in California)

The filter usually slides into a slot where air enters the unit.

At the Bottom or Side of the Unit

Some systems have the filter at the base or side of the furnace or air handler, especially in garages or closets.

Can't Find It?

If you're unsure:

  • Check for a removable panel near where air is pulled into the system
  • Look for arrows or labels that say "air flow" or "filter"
  • If it still isn't obvious, don't worry — many people need help the first time
2

Find Your Filter Size

Once you remove the filter, the size is usually printed directly on the frame.

It will look something like this:
16 × 25 × 1
Width × Height × Thickness (in inches)

Most homes use 1-inch thick filters, which is what FilterBuddy provides.

If the Size Isn't Printed or Is Hard to Read

You can measure it yourself:

↔️
Measure width
↕️
Measure Height
📏
Measure thickness

Round down to the nearest whole inch if needed.

Example:

16.25 × 25.5 × 1 → choose 16 × 25 × 1

Getting close is important — filters that are too big or too small won't work properly.

A Few Helpful Tips

  • Only use one filter unless your system clearly has multiple return vents with filters
  • Never stack filters
  • Always note the airflow arrow on the side when installing
  • If your filter looks dark, dusty, or warped — it's overdue

If your system has more than one filter and you're unsure, we can help.

Still Not Sure? We've Got You.

You're not expected to know this already — most people don't. If you're unsure where your filter is or what size you need, reach out and we'll help you figure it out. That's part of what FilterBuddy is here for.

Clean air starts with the right fit — and it doesn't have to be complicated.