This study was conducted to analyze factors influencing the compressive strength test. The purpose is to introduce various factors affecting the accuracy of the compressive strength test in accordance with current standards and evaluate the effect of some effective parameters such as equipment (loading rate of automatic compression machine, jolting or vibrating), mortar preparation, sample preparation, etc. To check the reproducibility of the compressive strength test a program was developed to assess the possible modes through changes in loading rate, standard sand, sample preparation, and operator. The changes of each parameter were measured within 2, 7 and 28-day interval, while other conditions were considered as constant based on the EN 196-1 and ISIRI 393 standards. According to the test results, the most important factors in creating the difference in results are the type of the sand and loading rate. The changes in the reproducibility percentage using different sands with softer grains increases the coefficient of variation and reduced performance of the test. Also in some cases, with increasing the loading rate up to 40%, the compressive strength of 28 days is increased by 13%.