Absolute pressure

Absolute pressure is the pressure of a fluid relative to an absolute vacuum (i.e. deepest darkest space). Absolute pressure is often determined from gauge pressure by adding the ambient barometric pressure:

Pa = Pg + Pb

e.g. a pressure gauge on a machine reads 130 kPa, while the barometer next to it reads 1016 hPa. The absolute pressure as measured by the machine would be:

130kPa + 1016 hPa = 130,000 Pa + 101,600 Pa = 231,600 Pa = 231.6 kPa