Standard Atmospheres to Millibars (atm to mbar)
1 standard atmosphere equals 1,013.25 millibars exactly.
How to convert standard atmospheres to millibars
To convert standard atmospheres to millibars, multiply the number of standard atmospheres by 1,013.25. This factor is exact. To go the other way, multiply millibars by 0.0009869232667 (rounded).
millibars = standard atmospheres × 1,013.25
Example: 10 standard atmospheres = 10,132.5 millibars.
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
Millibar (mbar)
One thousandth of a bar, equal to one hectopascal. Standard atmospheric pressure is 1,013.25 mbar.
Millibar and hectopascal are the same pressure with different pedigrees. The millibar was introduced alongside the bar by Vilhelm Bjerknes, and meteorologists worldwide adopted it because the values are convenient: a thousandth of a bar puts ordinary air pressure near 1,000. Standard atmospheric pressure is 1,013.25 millibars.
When SI came in, some meteorologists switched to hectopascals, which carry exactly the same numbers. The millibar did not vanish, though. The symbol mb is still common, and Americans know the unit from US hurricane and cyclone reports.
A few readings give the scale. The record-low non-tornadic pressure of 870 hPa in Typhoon Tip in 1979 equals 870 millibars, and falling pressure of about 12 hPa per 100 meters of altitude means a mountain road can shave tens of millibars off a barometer reading in a short climb.
1 millibar = 100 pascals (exactly).
Sources: Wikipedia: Bar (unit); Wikipedia: Hectopascal; Wikipedia: Atmospheric pressure
Related conversions
- Millibars to standard atmospheres (reverse)
- Standard atmospheres to pascals
- Standard atmospheres to kilopascals
- Standard atmospheres to bars
- Standard atmospheres to PSI
- Standard atmospheres to hectopascals
- Standard atmospheres to megapascals
- 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 millibars
- Kilopascals to millibars
- Bars to millibars
- PSI to millibars
- Hectopascals to millibars
- Megapascals to millibars
- Torr to millibars
- Millimeters of mercury to millibars
- Inches of mercury to millibars
See all pressure units.