A method and a system for calibrating an X-ray photoelectron spectroscopy (XPS) measurement are described. The method includes using an X-ray beam to generate an XPS signal from a sample and normalizing the XPS signal with a measured or estimated flux of the X-ray beam. The system includes an X-ray source for generating an X-ray beam and a sample holder for positioning a sample in a pathway of the X-ray beam. A detector is included for collecting an XPS signal generated by bombarding the sample with the X-ray beam. Also included are a flux detector for determining a measured or estimated flux of the X-ray beam and a computing system for normalizing the XPS signal with the measured or estimated flux of the X-ray beam.