STP, an acronym for standard temperature and pressure, refers to an experimental condition consisting of a predetermined temperature and pressure that is used for measuring and documenting experiments. The most widely used standard condition refers to a temperature of 273.15 K and a pressure of 1 atmosphere.
Performing measurements and experiments at standard conditions allows for the direct comparison of obtained data. This is because the physical properties of gases and liquids, such as volume and density, can change depending on temperature and pressure. Standard conditions are necessary in certain industries as a reference to which related measurements, such as volumetric flow rate, are calculated. Without specifying the standard conditions, comparing one system's flow rate to another often leads to errors in determining performance.