Calculated Results
The calculator shows key pitot performance outputs directly below the header and above the form.
Pressure and Velocity Trend
Calculator Inputs
Choose a pressure input method, then provide fluid and geometry values. Large screens show three columns, smaller screens show two, and mobile shows one.
Example Data Table
This sample dataset shows how changing pressure difference affects velocity and flow for the same pipe and fluid assumptions.
| Case | ΔP (Pa) | Density (kg/m³) | Diameter (m) | Velocity (m/s) | Flow Rate (m³/s) | Reynolds Number |
|---|---|---|---|---|---|---|
| Low Airflow | 150 | 1.225 | 0.10 | 15.65 | 0.123 | 105,983 |
| Medium Airflow | 650 | 1.225 | 0.15 | 32.57 | 0.576 | 330,974 |
| High Airflow | 1600 | 1.225 | 0.20 | 51.11 | 1.605 | 691,690 |
Formula Used
ΔP = entered pressure difference
ΔP = (ρm − ρ) × g × h
V = C × √(2ΔP / ρ)
A = πD² / 4 or A = manual input
Q = A × V
ṁ = ρ × Q
Re = (ρ × V × D) / μ
Pt = Ps + ΔP
a = √(γRT) and M = V / a
These relations are most suitable for steady incompressible analysis. If Mach rises above about 0.30, compressibility effects become more important and a compressible correction may be needed.
How to Use This Calculator
- Select whether your pressure input comes from a direct differential pressure reading or a manometer height difference.
- Enter the flowing fluid density and viscosity. For air at room conditions, default values are already loaded.
- Provide pipe diameter. Keep area mode on automatic unless you already know the exact cross-sectional area.
- Enter static pressure if total pressure is needed.
- Provide temperature, gas constant, and specific heat ratio if you want Mach number.
- Click the calculate button. Results will appear above this form and below the header section.
- Use the CSV or PDF buttons to export the scenario for reporting or comparisons.
- Review the chart to see how velocity changes with differential pressure around your current operating point.
Frequently Asked Questions
1) What does a pitot tube measure?
A pitot tube measures stagnation pressure and compares it with static pressure. Their difference gives dynamic pressure, which can be converted into fluid velocity using Bernoulli-based relations.
2) When should I use the manometer mode?
Use manometer mode when the pitot setup reports a fluid column height difference instead of a direct pressure value. The calculator converts that height into differential pressure before computing velocity.
3) Why is fluid density important?
Velocity from a pitot tube depends on the ratio of pressure difference to density. A lower density produces a higher calculated velocity for the same differential pressure.
4) What is the pitot coefficient?
The pitot coefficient adjusts the ideal Bernoulli result to reflect real probe behavior, calibration, alignment, and installation effects. A value near 1.00 is common for well-calibrated arrangements.
5) Why does the calculator include Reynolds number?
Reynolds number helps describe the flow regime and provides context for velocity results. It also supports engineering checks where turbulence, profile shape, or probe performance matter.
6) Is Mach number always required?
No. Mach number is optional but useful for gas flows. It becomes more important when velocity rises and compressibility may influence pitot relations and measurement interpretation.
7) Can I enter area manually?
Yes. Manual area entry is helpful when the duct is non-circular, already corrected, or known from drawings. Otherwise, the calculator can derive area automatically from diameter.
8) What does the uncertainty result mean?
The uncertainty output estimates how pressure reading uncertainty affects velocity. Because velocity varies with the square root of differential pressure, velocity uncertainty is roughly half of the pressure uncertainty percentage.