# Absolute Pressure

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

A pressure at absolute zero can only exist in a total vacuum and any pressure above this is called absolute pressure.  Absolute pressure, abbreviated as $$p_a$$, is the amount by which the measured pressure exceeds a perfect vacuum.  It is specified as psia.  Absolute pressure is equal to 0 psia or -14.7 psig.

 $$\large{ p_a = p_g + p_{atm} }$$ $$\large{ p_a = p_g + p_v }$$ Where: $$\large{ p_a }$$ = absolute pressure $$\large{ p_g }$$ = gauge pressure $$\large{ p_{atm} }$$ = atmospheric pressure $$\large{ p_v }$$ = vacuum pressure Solve for: $$\large{ p_g = p_a - p_{atm} }$$ $$\large{ p_{atm} = p_a - p_g }$$