CFM & Airflow Calculator
Calculate the required airflow (CFM) for any room based on its size and recommended air changes per hour. Also determine duct velocity and velocity pressure for proper HVAC system sizing.
Results
Room Volume
2,400
cu ft
Required CFM
320
cubic ft / min
Duct Velocity
917
FPM
Velocity Pressure
0.052
in. w.g.
Duct velocity is moderately high. Consider a larger duct for quieter operation.
ACH Guidelines by Room Type
| Room Type | Recommended ACH |
|---|---|
| Bathroom | 8 |
| Kitchen | 15 |
| Bedroom | 6 |
| Living Room | 6 |
| Office / Study | 6 |
| Laundry Room | 9 |
| Garage | 6 |
| Basement | 4 |
| Server Room | 15 |
| Commercial Kitchen | 30 |
How to Use This Calculator
Enter the room dimensions in feet and select or type the desired air changes per hour (ACH). Then choose your duct shape and enter its dimensions to see the resulting duct velocity. Refer to the ACH guidelines table below for recommended values by room type.
Formula Used
Room Volume = L x W x H (cu ft). Required CFM = (Volume x ACH) / 60. Duct Area (round) = pi x (D/2)^2. Duct Velocity (FPM) = CFM / Duct Area (sq ft). Velocity Pressure = (V / 4005)^2 in inches of water gauge.
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Disclaimer
This calculator is for estimation purposes only. Results may vary based on local conditions, materials, and building codes. Always consult a licensed professional before making decisions based on these calculations. MyContractorTools is not responsible for any errors or omissions.