HVAC Filter Size Reference
Compare nominal and actual HVAC filter dimensions for common residential filter sizes.
Furnace/AC filters are labeled with a rounded "nominal" size, but the actual filter is usually about 1/4"–1/2" smaller in each dimension so it slides into the slot. Measure your old filter's actual size if you're unsure.
About this tool
HVAC Filter Size Reference is a single-purpose utility on instant.tw, a free toolbox of calculators, converters, generators, and quick lookups. Everything works in your browser — nothing is uploaded, nothing is stored on a server unless explicitly noted.
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