The properties of the rock mass, such as compressive strength and deformability of rocks, also have a direct impact on mining technology, the machinery used and its efficiency. For many years, work has been carried out on the widespread use of the ultrasonic method for determining rock strength properties. This method is characterized by simplicity of measurement and its accuracy increasing with the number of measurements. A very important advantage of this method is the possibility of multiple measurements, the short duration of the measurements and the almost immediate results, which can be presented in the form of a curve reflecting the relationship between compressive strength and the measured acoustic parameters. The article describes the development of research and the relationship between compressive strength and acoustic parameters such as volume density, longitudinal wave velocity and the product of volume density and longitudinal wave velocity. The analyses demonstrated the accuracy of the calculations based on the value of the coefficient of determination (R2). A new relationship between compressive strength and acoustic modulus was presented, and it has the highest accuracy. It was proposed that this new method can be used to calculate the compressive strength of all brittle materials using acoustic modulus.