Reynolds Number Calculator

Calculate the Reynolds number Re = ρVD/μ for pipe flow and determine the flow regime: laminar (Re < 2300), transitional (2300–4000), or turbulent (Re > 4000). Enter velocity or volumetric flow, pipe internal diameter, and fluid density and viscosity. Pick from a fluid library or enter custom properties.

Reynolds number is the gateway parameter for friction-factor selection - laminar flows use f = 64/Re, turbulent flows use the Colebrook-White correlation with pipe roughness.

Related calculators: friction loss, pipe sizing, unit converter. Read about friction models.