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Unconfined Compressive Strength (UCS) of the rock is one of the most crucial parameters in the analysis of geotechnical problems such as tunnel design, rock blasting and mechanical rock excavation. However, proper determination of UCS through direct experimental test is not always possible as it is difficult to obtain sufficient numberof rock samples from highly to moderate weathered rocks. In addition, Unconfined Compression Test (UCT) is time consuming and expensive. Indirect method of UCS estimation such as Schmidt Rebound Hammer Test which is a quick and inexpensive test can be used for predicting the unconfined compressive strength. This study investigates different correlations between UCS and Schmidt hammer. Hence a total number of 60 laboratory tests (UCT, Dry density, and Schmidt hammer) on 20 limestone core samples were conducted. Findings show a good agreement between the results of experimental studies and previous well established literatures. A new correlation with high accuracy level for UCS prediction of limestone rocks is proposed and the reliability of one the most widely used correlation in Malaysia (Millers correlation) for UCS prediction using Rebound hammer is examined. Results show the degree of reliability of Millers correlation is high enough and it is in close agreement with the new proposed correlation. However, being only a function of Rebound number (RL) is the advantage of the new proposed correlation over Millers correlation.