Reynolds Number Calculator
Laminar or turbulent flow test.
Enter your values
Enter the fluid density in kg/m³.
Enter the velocity in m/s.
Enter the pipe diameter in m.
Enter the dynamic viscosity in Pa·s.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Reynolds number
- 59,880
- Flow regime
- Turbulent
- Kinematic viscosity
- 0.000001 m²/s
- Velocity for Re = 2300
- 0.04609 m/s
Quick answer
The Reynolds number compares inertial to viscous forces; below 2300 flow is laminar, above 4000 turbulent.
Re = ρvD / μ
At a glance
| What it does | Laminar or turbulent flow test. |
|---|---|
| Category | Science |
| Inputs needed | Fluid density, Velocity, Pipe diameter, Dynamic viscosity |
| Main output | Reynolds number |
| Formula | Re = ρvD / μ |
| Cost | Free — no sign-up, no download |
How to use the Reynolds Number Calculator
- 1Enter fluid density and viscosity.
- 2Enter flow velocity and pipe diameter in SI units.
- 3Read the regime classification.
Inputs explained
- Fluid density(kg/m³)
- Enter the fluid density in kg/m³.
- Velocity(m/s)
- Enter the velocity in m/s.
- Pipe diameter(m)
- Enter the pipe diameter in m.
- Dynamic viscosity(Pa·s)
- Enter the dynamic viscosity in Pa·s.
Worked example
Using the values the calculator loads with:
Inputs
- Fluid density998 kg/m³
- Velocity1.2 m/s
- Pipe diameter0.05 m
- Dynamic viscosity0.001 Pa·s
Results
- Reynolds number59,880
- Flow regimeTurbulent
- Kinematic viscosity0.000001 m²/s
- Velocity for Re = 23000.04609 m/s
Frequently asked questions
Water at room temperature?
Density 998 kg/m³, viscosity about 0.001 Pa·s.
Why does the regime matter?
Turbulent flow mixes better but causes far higher pressure loss.
What do I need to enter into the Reynolds Number Calculator?
Just 4 values: fluid density, velocity, pipe diameter, dynamic viscosity. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Reynolds Number Calculator work out the answer?
The Reynolds number compares inertial to viscous forces; below 2300 flow is laminar, above 4000 turbulent. It applies the formula Re = ρvD / μ and shows the working so you can check each step by hand.
Is the Reynolds Number Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.