In this paper, we define a universal measure of macroscopicity $\beta$ in the form of, experimentally observed coherence time/ characteristic time required to repeatably distinguish the components of a quantum superposition state, to divide the quantum/classical (Q-C) boundary. The analysis shows that, for a matter-wave interferometer, covering systems from electron to macromolecular, the measure of its macroscopicity is expressed by β=pθd/8hbar, and it consistently yields β<1 by investigating the coherence data reported in the literature. The result implies that limited advancement has been made toward exploring the Q-C boundary in such experiments. Additionally, for a Ramsey-like interferometer, the measure of its macroscopicity is expressed as β=8π³αν0r²sν²sT/(9c²). After analyzing the reported experimental data, we find that a maximum value of β~300 is achieved in the vertical atomic fountain experiments. Therefore, searching the Q-C boundary in the atomic fountain may be a more proper direction.