Aim and background: The orthodontic diagnosis and treatment planning are the fundamental goals during the mixed dentition period. Numerous methods have been proposed to date. The study was designed to determine the mesiodistal (MD) widths of the lower permanent canines and premolars from Tanaka and Johnston, regression equation (RE) proposed for north Indian population (RE-NIP), Bernabé and Flores-Mir C, Moyers’, and Ling and Wong mixed dentition analysis (MDA) and to determine the correlation coefficients for the Eluru population. Materials and methods: The study population was selected using cluster random sampling. A total of 3,572 children were clinically examined from the Outpatient Department of Pediatric and Preventive Dentistry, St Joseph Dental College and Hospital, Eluru district, Andhra Pradesh. Out of these, 140 children aged 11–16 years were randomly selected for the study based on the inclusion and exclusion criteria. The MD width of permanent incisors, canines, premolars, and molars was measured with the help of a digital vernier caliper; summed up and compared with the above-mentioned REs. The data obtained were subjected to statistical analysis using SPSS version 22, employing Student's t-test, Pearson correlation coefficient, and Kruskal–Wallis test. Results: The RE-NIP underestimated the values, whereas the remaining equations overestimated the sum of permanent canines and premolars in both arches in the study population. Conclusion: The predicted values obtained from the abovementioned methods overestimated the actual values, and a new RE for the Eluru population should be suggested to better represent the size of unerupted canines and premolars. Clinical significance: Measuring the MD widths of the upper and lower permanent incisors and molars during the mixed dentition period from different REs will help a pedodontist in proper treatment planning to predict the MD width of unerupted canines and premolars.