What is millibar?
A millibar is a pressure unit equal to one thousandth of a bar. It is the standard unit for atmospheric pressure in meteorology and weather forecasting, particularly in aviation and marine contexts.
Real-world uses
Millibars are the traditional unit in meteorology for reporting atmospheric pressure, particularly in weather maps and hurricane tracking. Standard atmospheric pressure is 1013.25 mbar, and tropical cyclones can have central pressures below 900 mbar.
History
The millibar was introduced by Sir Napier Shaw in 1909 for meteorological use. It dominated weather reporting throughout the 20th century. Since 1982, the WMO has officially recommended hectopascals instead, though both represent exactly 100 Pa.
Common mistakes
Not realizing that 1 millibar = 1 hectopascal exactly. Meteorological services have largely switched to hPa, but the numerical values are identical. Also, assuming lower millibar values mean calmer weather—lower pressure often indicates storms.
What is megapascal?
A megapascal is a pressure unit equal to one million pascals. It is used for measuring high pressures in industrial hydraulics, structural materials testing, and deep-sea and geological applications.
Real-world uses
Megapascals are used for concrete compressive strength (typical structural concrete is 20–40 MPa), steel tensile strength (mild steel ≈ 250 MPa yield), and hydraulic system pressures. Geologists use MPa for rock stress and tectonic pressure at depth.
History
The megapascal became a standard engineering unit with the global adoption of SI. It provides a convenient scale for material strength and high-pressure applications, replacing older units like kgf/cm² and ksi (kilopounds per square inch) in most countries.
Common mistakes
Confusing MPa with kPa—they differ by a factor of 1,000. Specifying concrete strength as 30 kPa instead of 30 MPa would describe an impossibly weak material. Also, 1 MPa = 1 N/mm², a useful equivalence often forgotten.
When is this conversion used?
Converting millibar to megapascal is useful in the pressure domain when comparing values across different measurement standards or applying formulas that require a specific unit.
Worked examples
1 millibar = 0.0001 megapascal
1 megapascal = 1,000,000 pascal
How to convert millibar to megapascal
To convert millibar to megapascal, multiply the value by 0.0001.
To convert megapascal back to millibar, multiply by 10,000.
Measurement standards
The pascal (Pa) is the SI derived unit of pressure, defined as one newton per square metre. The World Meteorological Organization mandates the hectopascal (hPa) for atmospheric pressure reporting in aviation and weather services.
Did you know?
The pressure at the bottom of the Mariana Trench, nearly 11 km deep, exceeds 1,086 bar — over a thousand times atmospheric pressure. At this depth, water is compressed by about 5%, making it measurably denser than at the surface.
Quick reference: millibar to megapascal
| millibar | megapascal |
|---|---|
| 0.1 | 0.00001 |
| 0.5 | 0.00005 |
| 1 | 0.0001 |
| 2 | 0.0002 |
| 5 | 0.0005 |
| 10 | 0.001 |
| 25 | 0.0025 |
| 50 | 0.005 |
| 100 | 0.01 |
| 250 | 0.025 |
| 500 | 0.05 |
| 1,000 | 0.1 |
Common values
| millibar | megapascal | |
|---|---|---|
| Car tyre | 2,200 millibar | 0.22 megapascal |
| Standard atmosphere | 1,013.25 millibar | 0.101325 megapascal |
| Blood pressure (systolic) | 160 millibar | 0.016 megapascal |
| Deep-sea submersible | 1,100,000 millibar | 110 megapascal |
| Bicycle tyre | 6,200 millibar | 0.62 megapascal |