When is it useful?
Schmidt number compares momentum diffusion with molecular mass diffusion. It is a mass-transfer counterpart of Prandtl number, useful for a dissolved or gaseous species carried by a flowing fluid.
Formula and inputs
Enter dynamic viscosity μ in Pa·s, fluid density ρ in kg/m³, and molecular diffusivity D of the particular species in m²/s. Since ν = μ/ρ, the same ratio can be written Sc = ν/D. The species and medium both affect D.
Open this calculatorWorked example
With μ = 0.001 Pa·s, ρ = 1000 kg/m³, and D = 1×10⁻⁹ m²/s, Sc = 0.001 ÷ (1000 × 1×10⁻⁹) = 1000.
Interpreting the result
For these chosen inputs, momentum diffusivity is 1000 times the species’ molecular diffusivity. Sc is a comparison ratio, not a concentration profile or mass-transfer rate.
Limits and cautions
Use a diffusivity appropriate to the species, medium, and temperature. Substituting turbulent diffusivity for molecular D changes the interpretation.
Formula and concept reference: NC State — marelac reference, Schmidt number. We created the sample inputs and calculations for this guide.