HVAC airflow reference table
Formula and unit scope
CFM = room volume (ft³) × ACH ÷ 60
ACH = CFM × 60 ÷ room volume (ft³)
m³/h = CFM × 1.69901082
ACH = CFM × 60 ÷ room volume (ft³)
m³/h = CFM × 1.69901082
These formulas relate volume flow to room volume or metric volume flow. They do not provide a universal ventilation rate, supply-air quantity, fan selection, or duct design criterion.
Room-volume lookup examples
| Room volume | 3 ACH | 6 ACH | 10 ACH |
|---|---|---|---|
| 960 ft³ | 48 CFM | 96 CFM | 160 CFM |
| 1,600 ft³ | 80 CFM | 160 CFM | 267 CFM |
| 2,400 ft³ | 120 CFM | 240 CFM | 400 CFM |
| 4,800 ft³ | 240 CFM | 480 CFM | 800 CFM |
CFM to metric lookup
| CFM | m³/h |
|---|---|
| 50 | 85.0 |
| 100 | 169.9 |
| 240 | 407.8 |
| 500 | 849.5 |
| 1,000 | 1,699.0 |
How to use this table
- Measure or calculate the actual room volume, including ceiling height.
- Use the CFM/ACH relationship only after choosing an airflow target from the applicable design or ventilation basis.
- Identify the air stream: supply, return, exhaust, outdoor, or recirculated.
- For ducts, continue with area, velocity, friction, fittings, and available fan pressure.
Limits and source context
ASHRAE treats ventilation, infiltration, internal gains, and system effects as distinct components in HVAC design. An ACH conversion alone cannot establish air quality, comfort, humidity control, or code compliance. Confirm project requirements and equipment performance with a qualified professional.
FAQ
Does this select a fan?
No. Fan selection also requires system resistance, controls, operating point, sound, and performance data.