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Reynolds Number Calculator

Calculate Reynolds number and classify flow as laminar, transitional, or turbulent with common fluid presets

Reynolds Number Calculator

Re = ρvD/μ = vD/ν  ·  Laminar <2300 · Transition 2300–4000 · Turbulent >4000

Use kinematic viscosity ν instead of ρ and μ

Reynolds Number

4.9810e+4

49,810

Flow Regime

Turbulent

Re > 4000 — chaotic, well-mixed turbulent flow

Formula

Re = ρvD/μ = 998.2 × 1 × 0.05 / 0.001002

= 49810

How to Use This Calculator

1

Select a fluid preset or enter custom properties

Choose water, air, or another common fluid to auto-fill density and viscosity, or enter custom fluid properties.

2

Enter flow parameters

Input the flow velocity, characteristic length (pipe diameter or plate length), and units.

3

Read the Reynolds number and flow regime

The calculator computes Re = ρVL/μ and classifies the flow as laminar (Re < 2,300), transitional, or turbulent (Re > 4,000).

Formula Reference

Reynolds Number

Re = ρVL / μ = VL / ν

Variables: ρ = fluid density, V = flow velocity, L = characteristic length, μ = dynamic viscosity, ν = kinematic viscosity

When to Use This Calculator

  • •Use the Reynolds Number Calculator when solving homework or exam problems that require quick numerical verification of your hand calculations.
  • •Use it during the design phase to rapidly iterate on parameters before running detailed finite element simulations.
  • •Use it when reviewing a colleague's calculation or checking a vendor's data sheet for plausibility.
  • •Use it to generate reference data for a technical report or presentation without manual computation.

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