High‐pass filtering is often used to remove long‐period noise of ground motions and obtain reliable spectral displacements at long periods. In previous studies, the filter cutoff period was often determined by visual inspection to ensure that the velocity and displacement time histories of the filtered ground motion have physically reasonable features. As a consequence, the effects of subjectivity were significant. For this, a quantitative method to determine the high‐pass filter cutoff period is presented in this article. The approach uses the wavelet multiresolution analysis to obtain the representation of the long‐period contents of ground motions. The ratio () of the peak ground acceleration of the equivalent long‐period contents obtained by the wavelet multiresolution analysis to the peak ground acceleration of the corresponding original ground motion is used as the quantitative parameter. The analysis results indicate that removing the long‐period contents with can yield reasonable time histories and response spectra. Furthermore, the comparison between the cutoff periods calculated by the quantitative method and those provided by the Next Generation Attenuation (NGA) West2 research project is presented.