Concrete is the most used material in construction. The most commonly used parameter for controlling the quality of concrete, which is measured in the most or all of the projects, is the compression strength of samples taken from fresh concrete in specific periods for each project. In this regard, in different structures, different compression strength classes are defined, which is usually the main parameter for verifying the structural specifications. In projects, one or two specimens are often tested at the age of 3 or 7 days, and two or three specimens at specific strength age (28, 42,...). It has been always questioned that how many percent of specific strength of concrete is gained in earlier ages. In this regard, references like Section 9 of the National Building Regulations have provided coefficients that show the relationship between compression strength of different ages based only on the type of cement. Also, in some articles and references, more advanced relationships, considering other factors affecting the strength of concrete, are provided. In this article, an attempt has been made to review the relationships and criteria provided by other references and articles at first. Then, by using a large number of data obtained in different temperature conditions and different strength grades which have been tested by a team of laboratories in a project in Iran and using cement type 2, has been proved that the strength development from early ages to the ages of specific strength, depends on a variety of factors, and cannot be considered a constant coefficient for all concrete made with even one type of cement (e.g., Section 9 of the National Building Regulations of Iran).