Outside Air CFM (Ventilation) Calculator

Calculate minimum outside air required for ventilation per ASHRAE 62.1 simplified method.

Calculator

Number of occupants

CFM/person

Floor area (ft²)

CFM/ft²

Minimum outside air

0.0 CFM

Enter values above and click calculate.

How It Works

This calculator determines the required outside air based on occupany and floor area using standard ventilation guidelines.

Outside Air (CFM) = (People × CFM/person) + (Area × CFM/ft²)

Where:
People = number of occupants in the space
CFM/person = airflow required per person (default: 7.5 CFM/person)
Area = floor area in square feet
CFM/ft² = airflow required per square foot (default: 0.06 CFM/ft²)

The calculator adds the ventilation required for occupants and the ventilation required for the space area to determine the total outside air requirement. Default values are based on typical office ventilation standards but can be adjusted for different occupany types.

Typical CFM/person by occupancy type:
Office spaces: 5–7.5 CFM/person
Classrooms: 10–15 CFM/person
Retail spaces: 7.5–15 CFM/person
Residential: 7.5 CFM/person