That pressure (force per unit area) recorded when the height of a column of mercury is reduced to standard gravity and temperature. It is the pressure exerted by a column of mercury 760 mm high, of density 13 595. 1 kg m⁻³, subject to a gravitational acceleration of 9. 80665 m s⁻², and equals 1013. 25 hPa. This is a sea level consideration at 45°N latitude.