Laplace pressure

The Laplace pressure (curvature pressure, capillary pressure) is the differential pressure between the inside and outside of a curved surface. According to the Young-Laplace equation, this pressure p depends on the surface tension σ and the radius of curvature r (for a sphere) or the main radii of curvature r1 and r2 (for a surface with any curvature):

Some methods for measuring surface tension or interfacial tension use the Laplace pressure directly or indirectly, e.g. the bubble pressure method and the pendant drop method.