# Absolute Pressure

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

A pressure at absolute zero, abbreviated as $$p_a$$, can only exist in a total vacuum and any pressure above this is called absolute pressure.  Absolute pressure 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.

## absolute pressure formulas

 $$\large{ p_a = p_g + p_{atm} }$$ $$\large{ p_a = p_g + p_v }$$

### Where:

 Units English Metric $$\large{ p_a }$$ = absolute pressure $$\large{\frac{lbf}{in^2}}$$ $$\large{Pa}$$ $$\large{ p_g }$$ = gauge pressure $$\large{\frac{lbf}{in^2}}$$ $$\large{Pa}$$ $$\large{ p_{atm} }$$ = atmospheric pressure $$\large{\frac{lbf}{in^2}}$$ $$\large{Pa}$$ $$\large{ p_v }$$ = vacuum pressure $$\large{\frac{lbf}{in^2}}$$ $$\large{Pa}$$