Gauge Pressure

Gauge Pressure

Gauge pressure is the pressure above atmospheric pressure.

$P_g = P_{atm} + \rho g h$

For example, with water ($\rho = 1000 \, \text{kg/m}^3$, $g = 10 \, \text{m/s}^2$, $h = 0.05 \, \text{m}$):

$P_g = 100{,}000 + 1000 \times 10 \times 0.05 = 100{,}500 \, \text{Pa}$

In mmHg units:

$P_g = 760 + 50 = 810 \, \text{mmHg}$

At the same level in a liquid, pressures are equal: $P_A = P_B$.