How bathroom CFM sizing works
Area rule, moisture factors, and NO_MATCH.
Bathroom exhaust fan sizing
Bathroom exhaust CFM calculator
Enter bathroom floor area and moisture load. Get CFM demand, then an 80 / 110 / 130 CFM class — or NO_MATCH. Duct length still matters.
Bathroom exhaust fan sizing
Result
CFM demand = area × moisture (1.0 / 1.25 / 1.5). Classes: 80 · 110 · 130 CFM.
From measurement to decision
Open the full calculator
Same tool with room for examples.
80 / 110 / 130 classes
When each CFM class fits — and when none do.
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