In this study, the calibration properties of volatile organic compounds (VOCs) were evaluated using two different types of sample transfer approaches for gas chromatography with mass spectrometry (GC-MS), [i.e., direct injection (DI) and solid-phase microextraction (SPME)]. The calibration of liquid-phase VOCs conducted by both approaches showed that the sensitivity of the SPME method is two to three times lower than that of DI. If such a comparison was extended further to gas phase standards, the relative dominance of DI was more prominent by approximately a single order of magnitude than SPME. The basic response characteristics of GC-MS, when assessed for a given compound (X) against a reference compound of toluene (T), showed an increase in the response factor ratio [R(X/T)] as a function of the carbon number [C(X/T)], regardless of injection method. This relationship was useful to roughly predict the concentrations of certain compounds in the absence of a standard for their calibration.