Is a 50 CFM bathroom fan enough?

A 50 CFM fan meets minimum code for bathrooms up to 50 sq ft. For a standard 8x10 bathroom (80 sq ft), 80 CFM is more appropriate. For a master bathroom with a separate shower and soaking tub, 150-200 CFM is typically needed. Bigger is better — an oversized fan is more effective and quieter than a small fan running at its limit.

What is a sone rating?

Sones measure the perceived loudness of a fan. Lower sone = quieter. 0.3 sones is nearly silent. 1.0 sone is very quiet, similar to a refrigerator. 3.0 sones is noticeably loud. Most new fans are rated 0.3-1.5 sones. Older fans were often 3-4 sones. Upgrading to a quiet fan (under 1.0 sone) is one of the most appreciated bathroom upgrades.

What Is CFM for a Bathroom Fan?

The Short Answer

CFM (cubic feet per minute) measures the volume of air an exhaust fan can move per minute. For bathroom ventilation, the HVI standard recommends 1 CFM per square foot of bathroom area for bathrooms under 100 sq ft, with a minimum of 50 CFM. For bathrooms over 100 sq ft, calculate by fixture: 50 CFM per toilet, 50 CFM per shower, 100 CFM per jetted tub. A large master bath with multiple fixtures may need 200-300 CFM. Undersized fans run constantly and still fail to adequately control moisture.

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What Is CFM for a Bathroom Exhaust Fan?

The Short Answer

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