MAXScanner thermal & fluid engineering
Rayleigh Number Calculator — Natural Convection Regime
Calculate Rayleigh number from Grashof and Prandtl numbers or from fluid properties for buoyancy-driven convection.
Last updated: September 17, 2026
Results
Enter non-negative Grashof and Prandtl numbers
Formula, example and assumptions
Ra=Gr·Pr=gβΔTL³/(να)·Pr.
Gr=1,000,000 and Pr=0.71 gives Ra=710,000.
- Property-based mode assumes positive transport properties.
- Transition thresholds depend on geometry and boundary conditions.
Frequently asked questions
What does Rayleigh number describe?
It compares buoyancy-driven transport with viscous and thermal diffusion effects.
How is Ra related to Pr?
Rayleigh number equals Grashof number multiplied by Prandtl number.