This method is for analyzing by gas chromatography mixtures of liquid hydrocarbons in the range of C5 through C20, using a column that separates components by boiling points. Procedures are provided for several applications, depending on the calibration used. These include, but are not limited to, (a) component distribution as defined by boiling points and corresponding carbon numbers, (b) determination of individual components resolved from a mixture of other components, and (c) analysis of a total sample wherein the identities of the major components or groups of components are known. Variations may be made as required, such as grouping of specific components by boiling ranges or extending the application to other ranges. The range of quantitation for a single component (or group of components) is 0.05 to 99.9 mass-%.