# Boundary layer thickness (For laminar boundary layers over a flat plate)

## Description

The boundary layer thickness is the distance across a boundary layer from the wall to a point where the flow velocity has essentially reached (99%)the 'free stream’ velocity.

Related formulas## Variables

δ | The overall thickness (or height) of the boundary layer (m) |

ν | Kinematic viscosity (m^{2}/s) |

x | The distance downstream from the start of the boundary layer (m) |

u_{0} | The freestream velocity (m/s) |