Boundary Layer Thickness Calculator

Local Reynolds number:

Transition typically occurs at Re_x ≈ 5×10⁵.

Laminar — Blasius solution:

Turbulent — 1/7 power-law (Prandtl):

Average drag coefficient over plate length L:

Mixed formula uses Re_x,crit = 5×10⁵ for the transition location.

Wall shear stress:

Where:

• δ = 99% boundary layer thickness [m]
• δ* = displacement thickness — effective streamline displacement [m]
• θ = momentum thickness — related to skin friction drag [m]
• H = shape factor = δ*/θ (2.59 laminar; 1.29 turbulent)
• C_f = local skin friction coefficient
• τ_w = wall shear stress [Pa]
• x = distance from leading edge [m]