Shore hardness (SH) has been accepted as a convenient and nondestructive method in measuring the hardness of rocks and widely used in rock mechanics since it can be correlated with other mechanical properties of weak rocks, such as uniaxial compressive strength (UCS). However, a need has arisen to propose a standard method as a measure of SH to minimize the errors when it is utilized as a predictor of the UCS as well as other mechanical properties of rocks. Over the last few decades, several studies have been conducted to predict consistent SH values using different procedures. However, the results of the tests can not be compared and analyzed in an overall way. Therefore, this experimental study was implemented to meet and discuss the demand for a new method to determine standardized SH values. In result, a new empirical equation was proposed to estimate size-corrected values of SH based on a critical specimen volume of 80 cm(3). (c) 2005 Elsevier Ltd. All rights reserved.