In chemistry, the term standard temperature and pressure (abbreviated STP) denotes an exact reference temperature of 0°C (273.15 K) and pressure of 1 atm (defined as 101325 Pa).
These values approximate freezing temperature and atmospheric pressure at sea level.
In aviation, standard temperature and pressure at sea level are 15°C and 29.92 in. Hg (1013.2 millibars). These values provide a reference for calculating various aircraft performance figures, such as endurance, range, airspeed, and fuel consumption. When used to calculate performance at any pressure altitude other than sea level, the temperature is adjusted using the dry adiabatic lapse rate.