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Free Bathroom Exhaust Fan CFM Calculator
Calculate the minimum CFM rating needed for a bathroom exhaust fan based on room dimensions and fixture count, following HVI and ASHRAE 62.2 guidelines. For bathrooms under 100 sq ft, the minimum is 1 CFM per sq ft (minimum 50 CFM). Larger bathrooms require 50 CFM per toilet, shower, or bathtub, plus 100 CFM for jetted tubs.
Frequently asked questions
What size exhaust fan do I need for my bathroom?
For bathrooms under 100 sq ft: minimum 1 CFM per sq ft (at least 50 CFM). For larger bathrooms: 50 CFM per toilet, shower, or tub, plus 100 CFM for jetted tubs.
How often should a bathroom fan run?
Run the fan during showers and for at least 20 minutes afterward to remove moisture and prevent mold. Many building codes require fans to run continuously or be on a timer.
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