The serviceability limit state-based design of laterally loaded pile foundation requires that the head displacement of the pile remains within a specified allowable limit. Laterally loaded rigid piles are analyzed by idealizing the surrounding soil as discrete springs. The equivalent soil spring constants are often developed empirically without considering three-dimensional pile–soil interaction. In the present study, the equivalent soil spring constants for laterally loaded rigid piles are derived from a continuum-based analytical model that captures the effect of three-dimensional pile–soil interaction. In the model, a rational soil displacement is assumed considering the kinematic compatibility with the pile displacement. The soil is assumed to behave elastically in a particular layer. The principle of virtual work is used to obtain the governing algebraic and differential equations for the pile and soil displacements, respectively. The accuracy of the method is verified against the results obtained from three-dimensional (3D) finite element analysis (FEA) and field test. A systematic parametric study on the effect of pile dimensions, soil layering, and soil properties on the spring constants is conducted for piles in single layer soil, two-layer soils, and single layer soils with the elastic modulus varying with depth. Fitted algebraic equations for the equivalent soil spring constants are developed through optimization that can be readily used by practicing engineers to calculate the response of rigid piles under lateral load and moment.