Pitot Tube Velocity Calculator

Input method

Differential pressure (ΔP)

Use measured dynamic pressure directly.

Stagnation and static pressure

Enter Pt and Ps for the probe.

Manometer (Δh and densities)

Compute ΔP from a U-tube reading.

Differential pressure ΔP

Used for incompressible velocity relation.

ΔP unit

Choose the unit that matches your instrument.

Stagnation pressure Pt

For compressible mode, use absolute pressure.

Pt unit

Static pressure Ps

For incompressible pitot, ΔP = Pt − Ps.

Ps unit

Fluid density ρ

Use density at operating temperature and pressure.

ρ unit

Manometer fluid density ρm

Typical: water ~1000, mercury ~13595 kg/m³.

ρm unit

Height difference Δh

U-tube level difference between columns.

Δh unit

Flow model

Incompressible

Best for liquids and low-speed gases.

Compressible (ideal gas)

Uses Pt/Ps and temperature for isentropic flow.

Gas and compressibility settings

Used only when compressible mode is selected.

V = √[(2γ/(γ−1))RT((Pt/Ps)^((γ−1)/γ) − 1)]

Gas preset

Preset fills a typical specific gas constant.

Specific gas constant R

Units: J/(kg·K). Set for your gas.

Heat capacity ratio γ

Use γ > 1. Typical air is about 1.4.

Temperature

Static temperature of the gas.

Temperature unit

Optional flow checks

Probe diameter D

Used only to compute Reynolds number.

D unit

Dynamic viscosity μ

Air at ~15°C is about 1.81 mPa·s.

μ unit

Gravity g

Used for velocity head and manometer ΔP.

Formula used

A Pitot tube measures stagnation pressure and compares it with static pressure. The difference is the dynamic pressure, which is related to flow speed.

Incompressible relation

ΔP = Pt − Ps

V = √(2ΔP / ρ)

Use for liquids and for gases at low Mach number.

Manometer relation

ΔP = (ρm − ρ) g Δh

Use when a U-tube converts the pressure difference into a height reading.

Compressible ideal-gas option

V = √[(2γ/(γ−1))RT((Pt/Ps)^((γ−1)/γ) − 1)]

Use when gas speed is high enough that density changes matter.

How to use this calculator

Select an input method that matches your measurement setup.
Enter density for the flowing fluid using correct units.
For Pt and Ps, ensure readings are consistent and stable.
Choose compressible mode for higher-speed gas flows.
If you have a manometer, enter Δh and manometer density.
Click Calculate to show results above the form.
Use the download buttons to export reports.

Example data table

Case	Method	Inputs	Density	Computed velocity
1	ΔP	ΔP = 500 Pa	ρ = 1.225 kg/m³	V ≈ 28.57 m/s
2	Pt and Ps	Pt = 101825 Pa, Ps = 101325 Pa	ρ = 1.225 kg/m³	V ≈ 28.57 m/s
3	Manometer	ρm = 1000 kg/m³, Δh = 60 mm, g = 9.80665	ρ = 1.225 kg/m³	V ≈ 30.95 m/s

Example velocities are rounded and depend on chosen density and units.

Practical notes

Align the probe with the flow to reduce cosine error.
Avoid placing taps near walls where velocity profiles distort readings.
For gases, use absolute pressures in compressible calculations.
If Re is very low, calibration factors may be needed.
Verify manometer fluid density at your temperature.

Formula used

How to use this calculator

Example data table

Practical notes

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