The measurement system analysis (MSA) approach is not only widely used in the life sciences industry and GMP consultancy to estimate, determine or evaluate measurement uncertainties, measurement errors or measurement accuracy. However, MSA also has limitations in its applicability when, for example, only individual verification tasks arise or a detailed view is required. The “Guide to the Expression of Uncertainty in Measurement”, GUM, provides a remedy. This international metrology guide provides the basis for a clear and transparent calculation of measurement uncertainty by creating a measurement uncertainty budget. The method based on the GUM is presented. The strengths and weaknesses of the two approaches are compared and recommendations are given for when which approach should be chosen in practice.