Pressure is exerted by fluids because of their weight. According to Georgia State University, static fluid pressure is exerted by the depth of the fluid, the density of the fluid and the acceleration of gravity.
The pressure due to liquid at a given depth depends upon the density of the liquid and the distance of the liquid to the bottom below the surface. According to Georgia State University, the equation for fluid pressure does not depend on the shape, total mass, surface area or volume of the liquid. Pressure is calculated by dividing the weight of the liquid by its surface area in a straight column. This equation only applies to liquid in a straight column because it is easier to calculate pressure in an unobstructed column. The pressure of a liquid calculated in a shape other than a column is more difficult to calculate. Because of this, pressure is usually measured in manometers in terms of liquid column height.
In addition, pressure at any depth is independent of direction, which means pressure is not a vector. In other words, the same pressure is applied throughout the entire liquid, not merely to one section of the liquid. This theory goes along with Pascal’s law, which states that any external pressure applied to a fluid is transmitted throughout the liquid and onto the walls of the vessel containing the liquid. For instance, when liquid is exposed to an open atmosphere, the absolute pressure of the liquid is increased by the pressure of the entire atmosphere pushing down on the surface of the liquid.