Comprehensive two-dimensional gas chromatography (GC x GC) is rapidly gaining importance for the analysis of complex samples. In order to predict chromatogram and optimize the operational conditions, the dead time of each dimension should be obtained exactly. Two methods to calculate the dead time of the second dimension were introduced. In the first method, based on the relationship between the time differences of a series of n-alkanes substances and the apparent retention times under different pressures, the true retention time can be calculated for non-synchronous GC x GC. The retention times of homologous series were used to calculate the dead time. Another rapid method to calculate the dead time of the second dimension is based on three or more apparent retention times in a single temperature programmed chromatographic run. The results show that the dead time of the second dimension can be calculated successfully by using the proposed methods and the deviation between the two methods is less than 0.05 s.