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.

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