Quantitatively estimating magnetotail flapping motion is critical to understanding and characterizing the dynamics of flapping behaviors. Such an estimation could be achieved in principle by the multipoint analysis of spacecraft tetrahedron, e.g. Cluster or MMS mission, but, owing to the inability of single-point measurement to separate the spatial-temporal variation of magnetic field, would be inadequate for a spacecraft. Since single-point missions dominate explorations of planetary magnetotail, we have developed a single-point method based on the magnetic field measurement that quantitatively estimates the parameters of flapping motion, including spatial amplitude, wavelength, and propagation velocity. A comparison with the application of multi-point analysis of Cluster demonstrates that our method can be reasonably be applied to infer the average parameters over a flapping period. Thus, this method could be applied widely to the “big dataset” accumulated by single-point spacecraft missions in order to study magnetotail flapping dynamics.