Gauge pressure and absolute pressure

In boiler technology, it is common practice to specify all pressure values as relative overpressure to atmospheric pressure of 1 bar.

The unit [bar] or [barg] is used in these contexts.

The conversion from gauge pressure to absolute pressure is therefore as follows:

Information

pabsolute = p + 1.01325 bar

Conversion from gauge pressure to absolute pressure:

Information

Normal conditions and standard conditions

Normal conditions (in accordance with DIN 1343):
pn = 101,325 Pa = 1.01325 bar = 1 atm
Tn = 273.15 K = 0 °C

Standard conditions (STP, IUPAC):
p0 = 100,000 Pa = 1.0 bar
T0 = 273.15 K = 0 °C

Standard environmental condition (SATP, IUPAC):
p0 = 100,000 Pa = 1.0 bar
T0 = 298.15 K = 25 °C