Mineral liberation has a strong effect on flotation performance. However, mainly due to stereological bias, the typical 2D scanning microscope mineralogical analysis is subject to limited representativeness and to high error propagation. In addition, grades calculated from the mineralogical distributions must be compatible with reconciled grades, estimated with mass balance calculations. Despite the existence of several stereological correction methods, only few approaches have been developed to solve this integration issue. Beta reconciliation method is able to minimise errors in liberation data while reconciling balanced grades with the grades calculated via the distribution of liberation classes. This is the first of a series of papers that aims at investigating and modelling flotation per size liberation classes. In this work, the beta adjustment method is detailed and optimized. Results from tests performed on a continuous chalcopyrite flotation circuit shows that the method provides the basis for a consistent balance, allowing to evaluate the flotation performance considering the size liberation classes.