The capillary pressure developed within a liquid droplet/film can be calculated using the Young–Laplace equation (e.g.):
where:
*  is the difference between the pressure across the liquid interface (Pa),
*  is the surface tension of the liquid (N/m),
*  is the unit normal pointing out of surface,
*  are the principle radii of curvature at any point on the free surface of the liquid film or droplet (m).
If the liquid wets the contacting surfaces then this pressure difference is negative i.e. the pressure inside liquid is less than the ambient pressure, and if the liquid doesn't wet the contacting surfaces then the pressure difference is positive and liquid pressure is higher than the ambient pressure.