Standard Atmospheres to Hectopascals (atm to hPa)
1 standard atmosphere equals 1,013.25 hectopascals exactly.
How to convert standard atmospheres to hectopascals
To convert standard atmospheres to hectopascals, multiply the number of standard atmospheres by 1,013.25. This factor is exact. To go the other way, multiply hectopascals by 0.0009869232667 (rounded).
hectopascals = standard atmospheres × 1,013.25
Example: 10 standard atmospheres = 10,132.5 hectopascals.
About these units
Standard Atmosphere (atm)
Exactly 101,325 pascals, the average pressure of the atmosphere at sea level.
A column of mercury about 76 cm tall was Torricelli's measure of the air, and the standard atmosphere began as exactly that: the pressure of 760 mm of mercury at 0 degrees Celsius under standard gravity. It was used as a reference for physical and chemical properties, and the Celsius scale set 100 degrees as the boiling point of water at that pressure.
In 1954 the 10th CGPM confirmed the standard atmosphere as exactly 1,013,250 dynes per square centimeter, which is 101,325 pascals, a definition that no longer depends on the properties of any substance.
In practice one atmosphere is about 1.01325 bar, 760 mmHg, 14.696 psi or 29.92 inHg, and roughly the pressure of 10.33 meters of water. Chemistry splits on it: until 1982 standard temperature and pressure used 1 atm, but that year IUPAC recommended a standard pressure of exactly 100 kPa instead.
1 standard atmosphere = 101,325 pascals (exactly).
Sources: Wikipedia: Standard atmosphere (unit); Wikipedia: Atmospheric pressure; Wikipedia: Evangelista Torricelli
Hectopascal (hPa)
100 pascals, equal to one millibar. The standard unit in weather forecasts and barometers.
Weather forecasters rarely think in pascals, and the hectopascal exists largely to avoid changing their numbers. When SI arrived, meteorologists generally switched from the millibar to the hectopascal, which equals exactly 100 Pa and exactly one millibar, so existing readings carried over unchanged. Observations are typically reported in hPa, following the World Meteorological Organization recommendation, though many scientific fields dislike the hecto prefix because they prefer steps of 1,000.
A typical sea-level reading is about 1,013 hPa. The lowest non-tornadic pressure ever measured was 870 hPa, in Typhoon Tip on 12 October 1979, and the highest sea-level pressure, 1,084.8 hPa, came at Tosontsengel, Mongolia, on 19 December 2001, at a station above 750 meters. At low altitudes, pressure drops about 12 hPa for every 100 meters you climb.
Aviation weather reports, such as the QNH in a METAR, use hectopascals or millibars in most countries, while the US, Canada and Japan quote altimeter settings in inches of mercury.
1 hectopascal = 100 pascals (exactly).
Sources: Wikipedia: Hectopascal; Wikipedia: Atmospheric pressure; Wikipedia: Pascal (unit)
Related conversions
- Hectopascals to standard atmospheres (reverse)
- Standard atmospheres to pascals
- Standard atmospheres to kilopascals
- Standard atmospheres to bars
- Standard atmospheres to PSI
- Standard atmospheres to megapascals
- Standard atmospheres to millibars
- Standard atmospheres to torr
- Standard atmospheres to millimeters of mercury
- Standard atmospheres to inches of mercury
- Standard atmospheres to gigapascals
- Standard atmospheres to kilopounds per square inch
- Standard atmospheres to millimeters of water
- Pascals to hectopascals
- Kilopascals to hectopascals
- Bars to hectopascals
- PSI to hectopascals
- Megapascals to hectopascals
- Millibars to hectopascals
- Torr to hectopascals
- Millimeters of mercury to hectopascals
- Inches of mercury to hectopascals
See all pressure units.