The SOLar-STellar Irradiance Comparison Experiment (SOLSTICE) on the SOlar Radiation and Climate Experiment (SORCE) observes both the Sun and stars in the ultraviolet (115-300 nm). Prior to launch, it was calibrated at the SURF-III synchrotron. Spectra from the International Ultraviolet Explorer (IUE) corrected to the white dwarf flux scale are in good agreement with SOLSTICE observations, validating the two completely independent methods of calibration. Measurements of stars in the SOLSTICE catalog are then used to transfer this calibration to the SPectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars (SPICAM) instrument. We describe the steps used to calculate the effective area for SPICAM to calibrate its stellar observations. Since only a handful of stars in the IUE archive have been converted to the white dwarf scale and many of them are relatively faint, the SOLSTICE catalog of bright stars can be an extremely useful resource for inflight calibration of ultraviolet spectrographs.