Hydrostatic stress (pressure) increases with depth due to the weight of the fluid column above. For an incompressible fluid: $P=P_{above}+\rho gh$

• If we consider the pressure relative to the surface (gauge pressure), it is simply $P=\rho gh$.
• $\rho$: Fluid density
• $g$: Acceleration due to gravity
• $h$: Depth below the surface This law forms the basis for Pascal's principle and the operation of hydraulic systems.