##### Inches of Mercury Inch of mercury (inHg and ″Hg) is a non-[[SI]] unit of [[Measurement]]  for [[pressure]]. It is used for [[atmospheric pressure|barometric pressure]]  in weather reports and aviation among other areas. It is the pressure exerted by a column of mercury 1 inch (25.4 mm) in height at the standard [[Acceleration Due to Gravity]]. Aircraft [[pressure altimeters|altimeters]] measure the relative pressure difference between the lower ambient pressure at [[altitude]] and a calibrated reading on the ground. In the United States, Canada and Japan, these altimeter readings are provided in inches of mercury, but most other nations use hecto[[pascal]]s. >Covered in: >Mentioned in: >References: [[WP Inches of Mercury|🌍]] >Required by: > >Related to: