Mbar

mbar stands for millibar, a unit of pressure defined as one thousandth of a bar. Specifically, 1 bar equals 100,000 pascals, so 1 millibar equals 100 pascals. The millibar has historically been widely used in meteorology and aviation to express atmospheric pressure and related measurements.

In practice, the millibar is practically interchangeable with the hectopascal (hPa) for meteorological purposes, since 1 hPa equals 1 mbar. The standard atmosphere at sea level is about 1013 hPa, which is also about 1013 mbar. In many contexts, including weather reports and aviation, pressure values are given in hPa or mbar, though the official SI unit is the pascal.

The millibar is a non-SI unit, but it remains common in weather science and operational contexts. Modern pressure sensors typically report in pascals or hectopascals, with voltages or digital readings converted to these units for analysis and interoperability.

Examples of typical ranges: at sea level, around 1013 mbar; at higher elevations, pressure falls roughly by a factor of two every 5.5 kilometers, so mountains and high plateaus exhibit several hundred millibars less pressure, and extreme summits may reach around 30–40 mbar. The term mbar is primarily of historical and meteorological relevance today, with hPa and Pa being the preferred SI-compatible designations.