CFM Calculator
Calculate airflow for a rectangular room and an air-change rate you specify.
Formula
Q (m³/h) = length × width × height × ACH; CFM = Q / 1.69901079552.
Room length: 12 ft · Room width: 10 ft · Ceiling height: 10 ft · Room volume ≈ (12 ft × 0.3048 m/ft)×(10 ft × 0.3048 m/ft)×(10 ft × 0.3048 m/ft) · Airflow in m³/h ≈ (33.98021591)×(4) · Airflow in CFM ≈ (135.9208636)÷(60×0.028316846592)
How to use
- Enter room length, width and ceiling height.
- Enter the required air changes per hour (ACH).
- Read airflow in CFM and m³/h.
Examples
- A 12 × 10 × 10 ft room at 4 ACH needs 80 CFM by volume arithmetic.
Frequently asked questions
Does the default ACH set a ventilation standard?
No. It is an example; select a target appropriate to the room and ventilation design.
Is this a fan selection calculation?
It excludes duct pressure, leakage, mixing and actual installed fan performance.
Does total airflow equal outdoor air?
Not necessarily. Recirculated air and outdoor air are different; use the flow type your target requires.
Sources
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