Aim and Objectives:The aim of the study is to compute a new formula for sex determination using maxillary arch width of a pediatric population of Namakkal district.Materials and Methods:The sample consisted of 146 females and 218 males of South Indian origin aged between 4 and 6 years. Alginate impressions of the upper and lower dental arch were made, and casts were poured immediately. A digital vernier caliper was used to obtain measurements. Arch width at canine, first molar and second molar for both maxilla and mandible were considered for measurement. Statistical analysis was performed using the Statistical Package for the Social Sciences Version 20.0 software.Results:The Student's t-test was used to find out the significance between male and female among the different predictor variables at P < 0.05. Significant sexual dimorphism was found in maxillary intercanine width and maxillary first and second intermolar width with conical discriminant function coefficient of 0.732, −0.177 and −0.244, respectively.Conclusion:The formula derived from the present study could be of great value in sex determination of pediatric populations of Namakkal district.