Experimental investigations to study the efficiency of using single non destructive test and combined methods to predict the concrete compressive strength have been conducted. Different concrete mixes including different types of coarse aggregates and mix proportions are considered. Concrete age's ranges from one to sixty days were covered. The statistical analysis of the results reveals that; with a reasonable correlation coefficient, rebound hammer and ultrasonic pulse velocity tests could be implemented individually to measure the compressive strength of concrete at age rang from one to sixty days.  Moreover, the use of both the rebound hammer and the ultrasonic pulse velocity tests as a combined method produces more reliable results that are closer to the actual compressive values compared to the use of one of the implemented methods individually. A proposed equation combines both rebound hammer and ultrasonic pulse velocity tests could be implemented securely for in situ concrete strength assessment has been established