The determination of the volume fraction of interfacial layers is very significant for assessing physical properties of complex multiphase materials. The majority of previous works focused on the volume fraction of interfacial layers around spherical and ellipsoidal particles, whereas little is known about generalized convex particles. In this work, an approximate theoretical estimation for the volume fraction of interfacial layers around polydisperse convex particles is developed, applying a theory of the nearest surface distribution functions and the specific surface area of convex particle systems. With numerical models for the volume fraction of interfacial layers around ellipsoidal and Platonic particles compared, the validity of the developed theoretical estimation is verified. The compared results reveal that the reliability of the approximate theoretical solution is favorable. Furthermore, such the formula can provide insight into the effects of microstructural geometrical characteristics of interfacial layers on physical properties of multiphase materials containing such interfacial layers. (C) 2013 Elsevier B.V. All rights reserved.