Converting Millimeters of Mercury to Millibars

This example problem demonstrates how to convert the pressure unit millimeters of mercury (mm Hg) to millibar (mbar). Millimeters of mercury is a pressure measurement usually associated with barometers and common in meteorology. A glass tube is sealed at one end and the open end is submerged into a pool of liquid mercury. Differences in air pressure on the mercury causes the level of the mercury to rise and fall inside the glass tube. The differences in height are measured in millimeters, which explains the name "millimeters of mercury". The bar is a pressure unit defined as 100 kilopascals and 1 millibar is 1/1000 bar.

Problem:

The average air pressure at sea level is 760 mm Hg. What is this pressure in millibars?

Solution:

1 mbar = 0.75218 mm Hg

Set up the conversion so the desired unit will be cancelled out. In this case, we want mbar to be the remaining unit.

pressure in mbar = (pressure in mm Hg) x (1 mbar/0.75218 mm Hg)
pressure in mbar = (760/0.75218) mbar
pressure in mbar = 1010 mbar

Answer:

The average sea level air pressure is 1010 mbar.