A unit of measurement typically used in the USA to report atmospheric pressure. A newer term for millibars used by the US scientists and the rest of the world is hectopascals (hPa). You may see the suction of a European vacuum cleaner related in millibars. To convert from millibars to inches of mercury, multiply it by 0.02953. Since mercury has a specific gravity of 13.546, you then need to multiply the inches of mercury by 13.546 to get inches of water lift. Alternately, you can simply multiply millibars by .04 to get inches of water lift.