This paper describes a numerical method for estimating the elastic modulus of cement paste. The cement paste is modeled as a unit cell, which consists of three parts: dehydrated cement grain, gel, and capillary pore. In the unit cell, the volume fractions of the constituents are quantified with a single kinetic function of the degree of hydration. The elastic modulus of cement paste was calculated from the total displacement of constituents when the uniform pressure was applied to the gel contact area in cement paste assumed a homogenous isotropic matrix. Numerical simulations were conducted through the finite element analysis of the three-dimensional periodic unit cell. The model predictions were compared with experimental results. The predicted trends agree with experimental observations. The approach and some of the results might also be relevant for other technical applications.