symbols, acronyms & abbreviations


hectopascal: hecto- + pascal, = 100 pascals. Used without a period. A symbol in SI, the International System of Units.

The World Meteorological Organization requires that barometric pressure be expressed in hectopascals.¹ “This is largely because one hectopascal equals one millibar (mbar), the formerly used unit.”


1. World Meteorological Organization.
Guide to Meteorological Instruments and Methods of Observation.
WMO-No. 8.
2008, updated 2010. Page I.1-9.
Available online at


Barry N. Taylor and Ambler Thompson, editors.
The International System of Units (SI) pdf logo
NIST Special Publication 330, 2008 Edition.

“United States version of the English text of the eighth edition (2006) of the International Bureau of Weights and Measures publication Le Système International d’ Unités (SI)” This publication is the definitive guide for the United States, but the ultimate authority is the original, French version. For the symbols for the prefixes, see page 29; those for the seven base units, page 23; and those for derived units, page 25. Symbols for non-SI units, some of which were formerly part of “the metric system”, such as the hectare, are given on pages 32, 34, 35, 37 and 38.


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