The fineness of a Portland cement and its chemical composition are the key factors in determining cement strength characteristics. This paper describes a study of the relationship between cement particle size distribution and surface area, and the effects of size distribution, surface area and chemical composition on concrete strength. A new correlation between particle size distribution and surface area has been established and models which include the size distribution and chemical composition as factors have been developed to predict cement strength based on a large data base generated from industrial surveys. These models are useful in optimizing clinker grinding by simulation. The relationship between the cement compressive strength determined by the concrete mix and mortar test methods is also discussed.