High Quality Content by WIKIPEDIA articles! Pressure (symbol: P) is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure. Pressure is an effect which occurs when a force is applied on a surface. Pressure is the amount of force acting on a unit area. The symbol of pressure is P. Pressure is a tensor quantity, and has SI units of pascal; 1 Pa = 1 N/m2, and has EES units of psi; 1 psi = 1 lb/in2. Pressure is transmitted to solid boundaries or across arbitrary sections of fluid normal to these boundaries or sections at every point.