Stalk rots are major fungal diseases of sorghum [Sorghum bicolor (L.) Moench] worldwide and cause significant economic loss. Conventionally, the length of stem lesions, produced by Fusarium thapsinum (FT; Fusarium stalk rot) and Macrophomina phaseolina (MP; charcoal rot), are measured to assess the degree of plant resistance. Genotypes with shorter lesion length (LL) are more resistant and expected to exhibit improved yield compared to susceptible genotypes. However, recent reports reveal inconsistent correlations between yield and LL, demonstrating the inadequacy of LL to predict yield under disease pressure. In this study, a new resistance-tolerance index (IndexRT) was used to rank 36 advanced sorghum male sterility maintainers (B-lines). IndexRT was formulated in such a way that a lower index value indicates increased disease resistance and reduced yield loss (i.e., greater tolerance) and vice-versa after infection. When ranked by LL, ARCH11035B, -11025B and -11011B were the best performing lines against Fusarium stalk rot, whereas the same lines ranked 1, 3, and 9, respectively, using IndexRT. Similarly, ARCH11018B, -11010B and -11014B had the lowest LLs respectively against charcoal rot, whereas the same lines were ranked 1, 4, and 30, respectively, based upon IndexRT. The LL- or IndexRT-dependent ranking differences of certain lines such as FT-inoculated ARCH11011B and MP-inoculated ARCH11014B indicated the effectiveness of deploying IndexRT for better evaluating sorghum lines against stalk rot diseases. There was no significant correlation between LL and IndexRT, revealing the independence of the two ranking systems. It is anticipated that this novel stalk rot screening procedure could be deployed by sorghum breeders for improved selection of parental lines.