MAXScanner thermal & fluid engineering
Fourier Number Calculator — Thermal Diffusion Time Scale
Calculate Fourier number from thermal diffusivity, elapsed time and characteristic length, or solve the corresponding diffusion time.
Last updated: September 17, 2026
Results
Enter positive diffusivity and length; leave exactly one of time or Fourier number blank
Formula, example and assumptions
Fo=αt/L²; t=Fo·L²/α.
α=1e-5 m²/s, t=100 s and L=0.05 m gives Fo=0.4.
- Thermal diffusivity is treated as constant.
- The characteristic length depends on the transient-conduction geometry.
Frequently asked questions
What does Fourier number measure?
It compares elapsed diffusion time with the thermal diffusion time scale across the chosen length.
Is Fourier number dimensionless?
Yes.