Standard Temperature and Pressure (STP) is the nominal conditions of temperature and pressure in the atmosphere at sea level that is important to physicists, chemists, engineers, and pilots and navigators. The Standard Temperature is defined as zero degrees Celsius (0 °C), which translates to 32 degrees Fahrenheit (32 °F) or 273.15 degrees kelvin (273.15 °K) that is essentially the freezing point of pure water at sea level, in air at standard pressure. The Standard Pressure supports 760 millimetres in a mercurial barometer (760 mmHg) that is about 29.9 inches of mercury, and represents approximately 14.7 pounds per square inch (14.7 lb/in2). Imagine a column of air measuring one inch square, extending straight up into space beyond the atmosphere. The air in such a column would weigh about 14.7 pounds.

Related Definitions in the Project: The Engineering; Property and Unit