Fan CFM Airflow Calculator
Calculate required fan CFM (cubic feet per minute) for rooms, server rooms, workshops, and electronic enclosures.
Convert between CFM, CMH, and m³/min.
CFM (Cubic Feet per Minute) is the standard unit used to measure airflow rate in ventilation and cooling systems. Choosing the right fan size ensures adequate air exchange, temperature control, and equipment longevity.
The Basic Airflow Formula
For room ventilation:
Required CFM = Room Volume (ft³) × Air Changes Per Hour (ACH) / 60
Or equivalently: Required CMH (m³/h) = Room Volume (m³) × ACH
Where ACH is the number of times per hour the entire volume of air in the space should be replaced.
Recommended Air Changes Per Hour (ACH)
| Space Type | Recommended ACH |
|---|---|
| Bedroom | 6 |
| Living room / Office | 6–8 |
| Kitchen | 15–20 |
| Bathroom | 8–15 |
| Server room / Data center | 20–60 |
| Workshop with dust | 20–30 |
| Electronics enclosure (heat-critical) | Calculate from heat load |
| Grow room | 30–60 |
| Garage | 6–8 |
Electronic Enclosure Cooling
For cooling electronics based on heat dissipation:
Required CFM = (P × 3.16) / ΔT
Where:
- P = Power dissipated as heat (Watts)
- ΔT = Allowable temperature rise (°C), typically 10–20°C
- 3.16 = conversion constant for standard air at sea level
This gives you the minimum airflow to keep components at a safe temperature.
Unit Conversions
- 1 CFM = 0.0283 m³/min = 1.699 m³/h (CMH)
- 1 CMH = 0.589 CFM
- 1 m³/min = 35.31 CFM
Practical Note
Always add a 20–30% margin to your calculated CFM requirement. Fan performance curves show that rated CFM is measured at zero static pressure — actual system resistance reduces real airflow by 20–50%.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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