Absolute Pressure

Absolute pressure is the total pressure exerted on a surface, measured relative to a perfect vacuum where there is no air or other gases present. It combines the atmospheric pressure, which is the force exerted by the air around us, and any additional pressure from a contained fluid or gas. For example, if a tire gauge reads 30 psi, that is gauge pressure; adding the atmospheric pressure (around 14.7 psi at sea level) gives the absolute pressure (~44.7 psi). Absolute pressure is important in scientific and engineering contexts because it provides a true measurement of pressure relative to a vacuum.