Reynolds Number Calculator
Calculate the Reynolds number for fluid flow to determine flow regime (laminar, transitional, or turbulent).
Published by:
isCalculator Editorial Team
Was this calculator helpful?
How to use this tool?
This calculator computes the Reynolds number (Re), a dimensionless value that predicts flow regime (laminar, transitional, or turbulent) in fluid dynamics.
Step-by-Step Guide
- Enter Fluid Density (kg/m³) – e.g., 1000 for water.
- Enter Flow Velocity (m/s) – e.g., 2 for a typical pipe flow.
- Enter Characteristic Length (m) – e.g., pipe diameter (0.1 m).
- Enter Dynamic Viscosity (Pa·s) – e.g., 0.001 for water at 20°C.
- Click Calculate or press Enter on any input.
Understanding the Result
- Re < 2300 → Laminar flow (smooth, orderly).
- 2300 ≤ Re < 4000 → Transitional flow (unstable).
- Re ≥ 4000 → Turbulent flow (chaotic, mixing).
Note: All inputs must be positive numbers. Use metric units only (kg/m³, m/s, m, Pa·s). The formula used is Re = (ρ × v × L) / μ.
Previous Results
| Result | Inputs | Date |
|---|
Frequently Asked Questions
The Reynolds number (Re) is a dimensionless quantity used to predict flow patterns in fluid mechanics. It is the ratio of inertial forces to viscous forces.
Typically, Re < 2300 indicates laminar flow, 2300 ≤ Re < 4000 indicates transitional flow, and Re ≥ 4000 indicates turbulent flow.
Density in kg/m³, velocity in m/s, characteristic length in meters, dynamic viscosity in Pascal-seconds (Pa·s).