Hydrostatic Pressure Formula |
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\( HP \;=\; \rho \cdot g \cdot h \) (Hydrostatic Pressure) \( \rho \;=\; \dfrac{ HP }{ g \cdot h }\) \( g \;=\; \dfrac{ HP }{ \rho \cdot h }\) \( h \;=\; \dfrac{ HP }{ \rho \cdot g }\) |
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| Symbol | English | Metric |
| \( HP \) = Hydrostatic Pressure (psi) | \(lbf \;/\; in^2\) | \(Pa\) |
| \( \rho \) (Greek symbol rho) = Fluid Density | \(lbm \;/\; ft^3\) | \(kg \;/\; m^3\) |
| \( g \) = Gravitational Acceleration | \(ft \;/\; sec^2\) | \(m \;/\; s^2\) |
| \( h \) = Fluid Height | \(ft\) | \(m\) |
Hydrostatic pressure, abbreviated as \(HP\) or \(P_h\), also called fluid pressure or gauge pressure, is the static pressure exerted at any point within a fluid at rest by the weight of the fluid column directly above that point, arising solely from gravitational body forces. This definition is used in fluid statics and applies to both liquids and gases in equilibrium, with the pressure acting normal to any surface in contact with the fluid. Hydrostatic pressure increases proportionally with depth and fluid density but remains independent of the container's horizontal dimensions, total fluid volume, or surface area. At any given depth in a connected body of fluid at rest, the pressure is identical at all points regardless of path, provided the fluid remains continuous and incompressible. This isotropy pressure acting equally in all directions stems from the absence of shear stresses in a static fluid and supports the transmission of applied forces through hydraulic systems.
The governing principle extends to Pascal's law, which states that an external pressure change applied to a confined incompressible fluid at rest is transmitted undiminished and equally to every point throughout the fluid and to its bounding surfaces. Hydrostatic pressure itself constitutes the baseline depth dependent component, with any superimposed applied pressure added uniformly.
