Science
Pipe flow rate
Multiply the internal cross-sectional area of a circular pipe by mean fluid speed to find volume flow per second and per minute.
Calculators / Science / Reynolds number
Reynolds number calculator
Compare inertial effects with viscous effects using density, mean speed, characteristic length and dynamic viscosity to obtain a dimensionless Reynolds number.
On this page
Reynolds number100,000
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How to calculate
Compare inertial effects with viscous effects using density, mean speed, characteristic length and dynamic viscosity to obtain a dimensionless Reynolds number.
Reynolds number = rho*v*d/mu
Worked example
Fluid density (kg/m³): 1000; Mean flow speed (m/s): 2; Characteristic length (m): 0.05; Dynamic viscosity (Pa·s): 0.001.
Reynolds number: 100,000 .
Assumptions and limits
Compare inertial effects with viscous effects using density, mean speed, characteristic length and dynamic viscosity to obtain a dimensionless Reynolds number. Use mean flow speed and the internal diameter. Reynolds number is dimensionless; any flow-regime threshold depends on geometry and conditions.
Results are rounded for display; calculations use unrounded values. Read our calculation methodology.
Understanding the result
Compare inertial effects with viscous effects using density, mean speed, characteristic length and dynamic viscosity to obtain a dimensionless Reynolds number.
When this tool is useful
Reynolds number = rho*v*d/mu
Understanding your inputs
| Input | What to enter |
|---|---|
| Fluid density (kg/m³) | Enter a number of at least 1e-12 and no more than 1000000000000. |
| Mean flow speed (m/s) | Enter a number of at least 0 and no more than 1000000000000. |
| Characteristic length (m) | Enter a number of at least 1e-12 and no more than 1000000000000. |
| Dynamic viscosity (Pa·s) | Enter a number of at least 1e-12 and no more than 1000000000000. |
Frequently asked questions
What assumptions does this calculation use?
Compare inertial effects with viscous effects using density, mean speed, characteristic length and dynamic viscosity to obtain a dimensionless Reynolds number. Use mean flow speed and the internal diameter. Reynolds number is dimensionless; any flow-regime threshold depends on geometry and conditions.
How is the result calculated?
Reynolds number = rho*v*d/mu