Understanding HVAC Filter Sizes

How to Find Your Size

Look at the existing filter — the size is printed on the frame (e.g., 20x25x1). Measure if the print has worn off. The three numbers are width x height x depth in inches.

Common Sizes

16x20x1 — small systems
16x25x1 — standard
20x20x1 — square systems
20x25x1 — most common
20x25x4 — media filter cabinets (changed every 6-12 months)

Never force a filter that doesn't fit — gaps let unfiltered air through.

Related Guides

How to Change Your HVAC Air Filter Annual Furnace Maintenance Checklist How to Clean Your AC Condenser Coils How to Replace Thermostat Batteries What HVAC Noises Mean and When to Worry

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