Pascal’s Principle (or Pascal’s Law) applies to static fluids and takes advantage of the height dependency of pressure in static fluids.

Named after French mathematician Blaise Pascal, who established this important relationship, Pascal’s Principle can be used to exploit the pressure of a static liquid as a measure of energy per unit volume to perform work in applications such as hydraulic presses.

Qualitatively, Pascal’s Principle states that pressure is transmitted undiminished in an enclosed static liquid. Quantitatively, Pascal’s Law is derived from the expression for determining the pressure at a given height (or depth) within a fluid.

Where p1 is the externally applied pressure, ρ is the density of the fluid, Δh is the difference in the height of the static liquid, and g is the acceleration due to gravity.

Pascal’s Law explicitly determines the pressure difference between two different heights (or depths) within a static liquid. As, by Pascal’s Law, a change in pressure is linearly proportional to a change in height within an incompressible, static liquid of constant density, doubling the height between the two points of reference will double the change of pressure, while having the height between the two points will half the change in pressure.