Inch of mercury

The inch of mercury (inHg or "Hg) was a non-SI unit of pressure. It was used for measuring barometric pressure, (the thickness of air), in weather forecasts, and aviation (flying), but was replaced by the pascal.

It is the amount of pressure that a column of mercury that is one inch tall has at 0 °C at the standard acceleration of gravity, or how fast things speed up as they are falling because of gravity.

1 inHg at 0 °C = 3,386.389 Pa.