Aim: This research aims to assess the reliability of various mixed dentition analyzes among the adolescents of Tamil Nadu and to devise a new regression equation by comparing the current mixed dentition analyzes. Settings and design: About 900 adolescents (13–18 years of age) were selected from the state of Tamil Nadu using stratified multistage sampling. Materials and methods: On the stone casts, the maximum mesiodistal width of permanent lower incisors, canines, premolars, and first permanent molars were measured. The measured values were analyzed and compared with existing mixed dentition analysis methods. Statistical analysis: Descriptive statistics were performed, and Pearson's correlation coefficient analysis was done. The p-value is kept at p < 0.05. Results: The teeth widths show sexual dimorphism and were larger in males than females. Moyer's (21.3 ± 0.6), Legovic's (21.1 ± 0.6), and Bachmann's (20.6 ± 0.6) methods significantly predicted the actual width (21.9 ± 1.3) in maxilla, whereas Moyer's (20.3 ± 0.5), Gross and Hussund's (21.0 ± 0.6), and Tanaka and Johnston's (20.3 ± 0.7) methods significantly predicted the actual width (20.3 ± 1.0) in mandible. Though these methods significantly predicted, they either overestimated or underestimated in the majority of cases. Hence, a regression equation was developed based on the results of the study. Conclusion: The basis of various mixed dentition analysis methods is the mesiodistal width of the teeth which is subjected to variability due to racial and ethnic factors. Therefore, the reliability of these analyzes should be analyzed in different racial groups. The regression equation developed in the study though holds good for a small set of samples, it should be tested on a large-scale for its reliability and accuracy.