Measuring uniaxial compressive and Brazilian tensile strengths (UCS and BTS) using standard laboratory tests are time consuming, tedious and expensive. Moreover, it requires a large number of well-prepared rock cores that is often not, particularly in soft or highly jointed rock masses. The purpose of this study is to compare the ISRM and ASTM suggested methods for determination of Schmidt hardness (Sh) and their performance to estimate the rock strength. For this, seven granite and marble samples were collected from the processing plants around Shiraz, Fars province, Iran. The Sh of samples was obtained based on ISRM and ASTM suggested methods. Thus, uniaxial compressive strength test (UCS) was used to determine of samples strength. Simple regression technique was applied to investigate of correlation between samples UCS and Sh. According to regression analysis, the UCS shows a better correlation with Sh based on ISRM, R2= 0.85, when compare with ASTM method, R2=0.74.