A simple theory is proposed to predict the effect of pressure for study of volume expansion of nanomaterials. Different possible forms of equation of state are discussed with their correlations. Only two input parameters, namely, the bulk modulus and its first pressure derivative, are required for calculations. We have considered a wide variety of nanomaterials, such as, CdSe (4.2 nm), Fe-Cu (14 nm), y-Al₂O₃ (67 nm), y-Al₂O₃ (37 nm), Ni (20 nm), Fe (10 nm), CeO₂ (cubic Fluorite phase) (15 nm), CeO₂ (Orthorhombic Phase) (15 nm), CuO (24 nm) and TiO₂ (rutile phase) (10 nm) to analyze the effect of pressure on them. The theoretical predictions for the given nanomaterials agree with the experimental results and the other theoretical models.