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🌀 Nusselt Number Calculator

Find the dimensionless Nusselt number, which compares convective to conductive heat transfer across a fluid boundary, from the convection coefficient, length scale, and thermal conductivity.

1
W/(m²·K)
2
m
3
W/(m·K)

What This Calculator Does

The Nusselt number (Nu) is a dimensionless quantity used in heat transfer engineering to describe the ratio of convective to conductive heat transfer across a fluid boundary layer. A higher Nusselt number indicates more effective convective heat transfer relative to pure conduction.

The Formula

The calculator uses the definition Nu = h × L / k, where h is the convective heat transfer coefficient of the fluid, L is a characteristic length of the surface or object (such as a pipe diameter or plate length), and k is the thermal conductivity of the fluid.

The Nusselt number is typically used alongside correlations (based on Reynolds and Prandtl numbers) to estimate h in the first place; this calculator performs the reverse or verification step once h, L, and k are known. For general engineering and educational reference.

Last reviewed August 2026