This paper describes a new strength time temperature prediction equation, which utilizes curing temperatures to improve the accuracy of estimates of long-term strength. To develop the model equation, existing data reported in the literature were collected and used. The effect of the diffusion shell, which happens during cement hydration, on the long-term strength as a function of the curing temperature was considered using the rate constant model. Temperature influence factors such as rate constant, limiting strength, and reaction coefficient, which are functions of curing temperature, were incorporated in the new equation. Temperature influence factors such as rate constant, limiting strength, and reaction coefficient, which are functions of curing temperature, were incorporated in the new equation. Verification of the proposed model was performed by regression analysis.