  We establish an objective scheme to determine the macroscopicity of quantum
mechanical superposition tests, which is based on the Bayesian hypothesis
falsification of macrorealistic modifications of quantum theory. The measure
uses the raw data gathered in an experiment, taking into account all
measurement uncertainties, and can be used to directly assess any conceivable
quantum test. We determine the resulting macroscopicity for three recent tests
of quantum physics: double-well interference of Bose-Einstein condensates,
Leggett-Garg tests with atomic random walks, and entanglement generation and
read-out of nanomechanical oscillators.
