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 torr?
A torr is a pressure unit equal to approximately 1/760 of an atmosphere. It is used in vacuum technology, low-pressure experimental physics, and blood pressure measurement in older clinical literature.
Real-world uses
Torr is used in vacuum technology, semiconductor manufacturing, and blood pressure measurement (mmHg ≈ torr). Vacuum chambers for electron beam welding operate at about 10⁻⁵ torr, and freeze-drying processes typically operate at 0.1–1 torr.
History
Named after Evangelista Torricelli, who invented the mercury barometer in 1644. The torr was defined to approximate the pressure exerted by 1 mm of mercury. It was formally standardized as 1/760 of a standard atmosphere.
Common mistakes
Assuming torr and mmHg are exactly the same—they are nearly identical but differ by about 0.000015%. For most purposes they are interchangeable, but ultra-precise vacuum work may require distinction.
When is this conversion used?
Converting between millibar and torr is common when working across metric and imperial systems, such as international trade, travel between countries with different measurement standards, or following instructions from a different region.
Worked examples
1 millibar = 0.75006168 torr
1 torr = 133.32236842 pascal
How to convert millibar to torr
To convert millibar to torr, multiply the value by 0.75006168.
To convert torr back to millibar, multiply by 1.33322368.
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 torr
| millibar | torr |
|---|---|
| 0.1 | 0.07500617 |
| 0.5 | 0.37503084 |
| 1 | 0.75006168 |
| 2 | 1.50012337 |
| 5 | 3.75030841 |
| 10 | 7.50061683 |
| 25 | 18.75154207 |
| 50 | 37.50308414 |
| 100 | 75.00616827 |
| 250 | 187.51542068 |
| 500 | 375.03084135 |
| 1,000 | 750.0616827 |
Common values
| millibar | torr | |
|---|---|---|
| Car tyre | 2,200 millibar | 1,650.13570195 torr |
| Standard atmosphere | 1,013.25 millibar | 760 torr |
| Blood pressure (systolic) | 160 millibar | 120.00986923 torr |
| Deep-sea submersible | 1,100,000 millibar | 825,067.85097429 torr |
| Bicycle tyre | 6,200 millibar | 4,650.38243276 torr |