When designing large-scale blasting operations, great consideration should be given to tailor the fragment size distribution in order to fulfil production requirements, while ensuring at the same time efficient and economical downstream operations such as loading, hauling, crushing and grinding. The selection of an optimum inter-hole delay time has been found to have beneficial effects in controlling fragmentation and face movement. The minimum response time T_min is reported in the literature as a key parameter for the selection of the appropriate inter-hole delay time. In this paper, data collected from 10 monitored full-scale blasts are used to investigate bivariate correlations between various design parameters. Further processing of the data using dimensional analysis resulted in the derivation of a mathematical relation that can estimate T_min as a function of blast design parameters and the desired size reduction ratio of blasting.