Reynolds Number Calculator
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
100% FreeRuns in your browserIntermediate
Enter Values
Enter your values and press Calculate to see results.
How to use this calculator
- Enter fluid density, velocity, characteristic length and dynamic viscosity.
- Read the Reynolds number.
How it works
Re = (density × velocity × length) ÷ dynamic viscosity.
Worked example
Water in a 50 mm pipe at 2 m/s. Re = 100,000 (turbulent).
Common mistakes
- Using kinematic viscosity where dynamic (Pa·s) is required.
- Picking the wrong characteristic length (pipe diameter for internal flow).
Frequently asked questions
What's laminar vs turbulent?
In pipes, Re below ~2300 is smooth laminar flow; above ~4000 it's turbulent, with a transitional zone between.
Related tools
Tip: Enter any known values to calculate the remaining results.
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