Kelvin equation

The Kelvin equation is used to calculate the onset/occurrence of capillary condensation

$\ln (\frac{p}{p_0})=-\frac{2{\gamma }_{lg}}{RT{\rho }_{l}H}$

Where p is the pressure, $p_0$ is the saturated vapour pressure, ${\gamma }_{lg}$ is the liquid-gas surface tension for the bulk fluid, ${\rho }_l$ is the density of the bulk fluid, R is the molar gas constant, T is the temperature and H is the pore or capillary width.