Calculation sequence
Step-by-step method
- Average velocity-pressure readings using the required traverse method.
- Convert average velocity pressure to average velocity using air density.
- Multiply average velocity by clear duct area.
MechanicalIntermediateAir Measurement
Pitot-Tube Airflow Calculator
Calculate air velocity and airflow from average velocity pressure, air density, and clear duct area.
Why it matters: Pitot traverses convert pressure measurements to velocity and require representative averaging and density awareness.
Calculated result
Engineering evaluation
Calculated airflow (Q)5,999 cfm
- Calculated average velocity (V)
- 1,500 fpm
- Entered clear duct area (A)
- 4 ft²
Engineering interpretation
The entered average velocity pressure indicates 1500 fpm and 5999 cfm through 4 ft².
Important limitations
- Confirm instrument orientation, density correction, traverse-point weighting, straight-run quality, leakage, and clear area.
Engineering knowledge center
Understand the calculation—not just the answer
Governing relationships
V = √(2Pv/ρ)
Q = VA
Current substitution
V = 1500 fpm; Q = 1500×4 = 5999 cfm.
Equation legend
Inputs and calculated quantities
- Pv
- Average velocity pressure — in. w.g. or Pa
- ρ
- Air density — lb/ft³ or kg/m³
- A
- Clear duct area — ft² or m²
- Q
- Calculated airflow — cfm
- V
- Calculated average velocity — fpm
- A
- Entered clear duct area — ft²
Applications
How this calculation is used
Building design
Check expected traverse velocity pressure at a design flow.
Construction
Plan traverse locations and instrument range.
Commissioning
Convert average measured velocity pressure to airflow.
Quality controls
Assumptions and limitations
Assumptions
- Entered values describe one stable operating condition and use consistent measurement boundaries.
- Fluid or air properties and geometric dimensions are representative of the evaluated system.
Limitations
- This is a preliminary evaluation and field-verification tool, not a final sizing or code-compliance determination.
- Manufacturer data, adopted codes, project criteria, and professional engineering review remain controlling.
Field use
Verification procedure
- Confirm the approved reference, measurement plane, and instrument calibration.
- Stabilize the system and record dimensions and operating data.
- Compare the calculated result with project documents and manufacturer data before disposition.
Common engineering mistakes
- Using outside dimensions rather than clear inside dimensions.
- Combining values from different loads, device positions, or measurement conditions.
Technical basis
References and source standards
- ASHRAE Handbook—FundamentalsCurrent handbook chapters covering duct design, fluid flow, heat transfer, insulation, and measurement; verify the licensed edition during professional review.
Engineering calculation disclaimer
These engineering tools are provided for educational, preliminary evaluation, field verification, and commissioning support. Results depend on the accuracy of user-entered information and the assumptions stated for each calculation. Every colored status and comparison is a screening indicator only; project criteria, contract requirements, applicable codes, manufacturer instructions, measurement uncertainty, and authorized engineering judgment govern. The tools do not replace project-specific engineering analysis or the judgment of a licensed professional engineer.
Read the full use and limitation statement