đ¨ Ventilation (CFM) Calculator
Calculate required airflow (CFM) for any room. Get exhaust fan recommendations and fresh air requirements per ASHRAE standards.
How to Use This Calculator
Select your room type from the dropdown â this presets the recommended air changes per hour. Enter the room dimensions (length, width, ceiling height). Adjust the number of occupants and air changes per hour if needed. The calculator provides CFM requirements and exhaust fan recommendations.
Understanding Your Results
CFM (Cubic Feet per Minute) measures airflow volume. Adequate ventilation removes moisture, odors, and pollutants. The ASHRAE fresh air requirement ensures healthy indoor air quality. When selecting an exhaust fan, choose one rated at or above your required CFM, and consider noise level (measured in sones â lower is quieter).
Frequently Asked Questions
What is CFM?
CFM stands for Cubic Feet per Minute, a measure of airflow volume. It tells you how much air is being moved by a fan, duct, or HVAC system in one minute.
How many CFM do I need for a bathroom?
The general rule is 1 CFM per square foot of bathroom space, with a minimum of 50 CFM. For bathrooms over 100 sq ft, calculate based on fixtures: 50 CFM per toilet, bathtub, or shower.
What are ASHRAE ventilation standards?
ASHRAE 62.2 requires minimum ventilation rates for residential buildings. The standard specifies 7.5 CFM per person plus 3 CFM per 100 sq ft of floor area for continuous ventilation.
How do I choose an exhaust fan?
Choose a fan rated at or above your calculated CFM requirement. Also consider noise level (measured in sones â 1.0 or less is quiet) and duct size compatibility.