First, the pressure (pressure) is the force borne by the unit area
Pressure: excellent pressure, gauge pressure, atmospheric pressure. Correlation: excellent pressure = gauge pressure + atmospheric pressure
Absolute Pressure: When the pressure is expressed as the difference from the complete vacuum. The actual pressure at the measuring point.
Gage Pressure: When representing the difference between its gas value and the atmospheric pressure in the region.
Atmospheric Pressure: Pressure Atmospheres Are pressures generated by atmospheric weights at a standard atmospheric pressure of 29.92" inch Hg.
Second, commonly used pressure conversion table

Note: The millimeter water column refers to the height of the water column in the 4 degrees Celsius state, and the millimeter Hg refers to the height of the water column in the 0 degree Celsius state. 1mmAg = 9.80665Pa = 0.0980665hPa

1atm = 760 mmHg = 1013hPa 1mmAg = 0.0735793mmHg