CMEM 2021 is the 20th International Conference in this well-established series on Computational Methods and Experimental Measurements. These successful meetings provide a unique forum for the review of the latest work on the interaction between computational methods and experiments. The principal objective of the conference has always been to provide to the international technical and scientific community, an opportunity to discuss the interaction between experimental measurements and computational methods with all associated topics. The continuous improvement in computer efficiency, coupled with diminishing costs and the rapid development of numerical procedures have generated an ever-increasing expansion of computational simulations that permeate all fields of science and technology. As these procedures continue to grow in magnitude and complexity, it is essential to validate their results to be certain of their reliability. This can be achieved by performing dedicated and accurate experiments, which have undergone constant and enormous development. At the same time, current experimental techniques have become more complex and sophisticated so that they require the intensive use of computers, both for running experiments as well as acquiring and processing the resulting data. The conference aims to address a wide variety of topics related to experimental and computational methods with emphasis on new applications and the latest developments.