Calculate the pressure inside the graduated cylinder it the height of the water is 5mm higher than the water in the trough. The atmospheric pressure is 760 mm Hg. Be sure to consider the difference in units: 1mm water does not equal 1 mm Hg. Start by converting the height pressure difference from mm H2O to mm Hg. You will find the following formula for pressure useful: P= d x g x h. d= density of liquid, g= gravity, h= height of liquid