Gamma-ray spectrometry with germanium detectors has been frequently applied for monitoring radioactive materials in sites of nuclear facilities. When cascade gamma-rays simultaneously interact with the detector, spurious peaks, so-called coincidence-sum peaks, and the full energy peaks with reduced intensity are observed in an apparent pulse height spectrum. Although there are some reports on the correction of the coincidence-sum effect, most of them cannot be easily applied for routine measurements. In order to make the correction simple, the method with the experimental formula of peak-to-total ratio given by the authors is presented. The intensities of full energy peaks corrected by the present method show good agreement with those by the method using total detection efficiencies.