To evaluate the thermal hazard of self-reactive substances in chemical processes, the time to maximum rate (TMR) of autocatalytic decomposition reaction of cumenehydroperoxide (CHP) was determined by calculations based on the results of isothermal measurement using DSC and heat conduction calorimeter. In addition, the factors affecting the calculated results were investigated. It was found that the TMR is affected by the catalytic action of the sample vessel metal. When this effect is taken into account in analyzing the experimental result, the predicted TMR shows a good agreement with the value determined using the adiabatic reaction calorimeter. The present study clarified that the proposed technique would enable the appropriate evaluation of thermal hazard of an autocatalytic reaction.