hPa
hectopascal
Pressureexact by definition
The hectopascal is exactly 100 pascals, and exactly equal to the millibar. It is the unit of surface atmospheric pressure in every modern meteorological service: standard sea level pressure is 1013.25 hPa, and a deep low might read 950 hPa.
| 1 hPa | 0.1 kPa |
Where the unit came from
Meteorology switched from millibars to hectopascals in the 1980s to become formally SI, having noticed that the two are numerically identical so no chart, no forecaster and no instrument dial had to change. It is the least disruptive unit conversion in history.
Solvers that use pressure