In standard practice, the most widely used test for cement concrete is compressive strength test using standard specimens which are kept and tested in a laboratory environment. However, the result of compression test done in a controlled laboratory environment can only show the adequacy of mix proportion to achieve the required strength. Unlike the laboratory specimens, the strength of in-place concrete is affected by many factors including compaction, curing, and ambient environmental conditions. Compressive strength test alone is a normal practice due to the absence of a standard method or model to relate the compressive strength result of the standard cured specimen with the strength of in-place cured concrete structures. In this research, mathematical models are developed to estimate compressive strength of in-place concrete putting five determining factors into consideration, i.e. curing method, curing duration, type and size of the building structure, and the result of standard compressive strength test. In order to determine the values of coefficients for equations and to study the effect of curing, 0.4, 0.5 and 0.6 water to cement ratios are considered. For each water to cement ratio, curing methods of wet burlap covering, plastic covering, water spraying and air curing were assessed. And also, for each curing method, 3, 7, and 14 days of curing duration were used. The formulae developed in this research can be used in order to take into account strength affecting factors. The use of these formulae could enhance the confidence of both contractors and consultants about their concrete work and it also can be used to compensate for the strength loss of in-place concrete due to curing, type and size of the structure while carrying out mix design. However, the formulae developed in this research work are only for the age of concrete on the 28th day. Therefore, this research must be continued to fully develop to make it applicable for all ages; especially, for those at early ages.