standard atmosphere

Convert to and from standard atmospheres to other major units of pressure

A unit of pressure = 101,325 pascals, approximately the value of atmospheric pressure at sea level. Symbol, atm. Also called the physical atmosphere. Compare technical atmosphere.

It was defined in the International Practical Temperature Scale of 1948¹ and subsequently adopted “for general use” by the 10th CGPM (1954, Resolution 4).² Some physicists had believed the 1948 definition only applied to thermometry.

An earlier definition of the standard atmosphere set it at 14.7 pounds per square inch (760.18 millimeters of mercury at a temperature of 0°C). The French used a slightly different definition: 760mm of mercury at a temperature of 0°C.³

According to the current national standard in the United States⁴, the standard atmosphere is not to be used. Kilopascals should be used instead.

1. Conférence Général des Poids et Mesures,
Comptes rendus des seances de la 9e Conférence Général des Poids et Mesures, Paris 1948.
Paris: Gauthier-Villars, 1949.

Pages 57 and 89.

2. Conférence Général des Poids et Mesures.
Comptes rendus des seances de la 10e Conférence Général des Poids et Mesures, Paris 1954.
Paris: Gauthier-Villars, 1955.

Page 79.

3. Latimer Clark.
A Dictionary of Metric and Other Useful Measures.
London: E & F.N. Spon, 1891.

4. IEEE/ASTM SI 10™-2002.
American National Standard for Use of the International System of Units (SI): The Modern Metric System.
New York: IEEE, 30 December 2002.

See Section 3.3.3.