Reynolds number calculator – Calculate the Reynolds number online
With this Reynolds number calculator, you can calculate the Reynolds number based on the flow
rate,
the internal diameter of the pipe, the density and the dynamic viscosity of the flowing medium.
The required material properties are automatically taken from the fluid table below, or you can enter your own
values.
The calculated Reynolds number can be used to determine whether the flow is laminar,
transitional or turbulent.
Inputs
mm
°C
You can enter your own temperature.
bar abs.
For gases, absolute pressure is taken into account.
Substance data
kg/m³
mPa·s
Substance data from the media table.
Result
Medium
–
Flow
–
Inner pipe diameter
–
Flow velocity v
–
Pipe cross-section A
–
Density ρ
–
Dynamic viscosity η
–
Temperature
–
Pressure
Pressure
–
Reynolds number Re
–
–
Substance Data Table
The values given for density and dynamic viscosity refer to the specified temperature and pressure in each case. For gases, density is also taken into account based on the absolute pressure.
| Medium | State of matter | Temperature | Pressure | Density ρ | Dyn. viscosity η |
|---|---|---|---|---|---|
| Water | Liquid | 20 | 1.013 | 998.2 | 1.002 |
| Water | Liquid | 40 | 1.013 | 992.2 | 0.653 |
| Water | Liquid | 60 | 1.013 | 983.2 | 0.466 |
| Air | Gas | 0 | 1.013 | 1.292 | 0.01716 |
| Air | Gas | 20 | 1.013 | 1.204 | 0.01813 |
| Air | Gas | 40 | 1.013 | 1.128 | 0.01908 |
| Ethanol | Liquid | 20 | 1.013 | 789.3 | 1.20 |
Author information
All technical articles published on durchfluss.info that name an author were personally written or technically reviewed by Harald Peters
Author of this article:
Harald Peters – Technical author specialising in flow measurement.
All technical articles published on durchfluss.info that name an author were personally written or technically reviewed by Harald Peters
Author of this article:
Harald Peters – Technical author specialising in flow measurement.
Last updated: 2026