This study aimed to measure the active mandibular range of motion (ROM) (mouth opening: MO; right and left lateral movements: RL and LL; protrusion: P) in Brazilian children of both genders and of various ages, weights, and heights, and to establish correlations among such variables. Study subjects (n = 303) were healthy boys and girls, with ages ranging between 6 and 14 years, who were regular students of a public school in the state of São Paulo. Analysis of variance and intra-class correlation coefficients were considered significant for p < 0.05. Weak significant correlations were observed between mandibular ROM and age, height, and weight. No statistically significant differences (p > 0.05) were observed regarding mandibular ROM between gender groups. Mean mandibular ROM values showed significant increases (p < 0.05) in relation to age, height, and weight, except for RL (p > 0.05), in the studied age range. Significantly smaller (p < 0.05) mean mandibular ROM values were observed for the intervals of 6 and 7 years of age, 1.15-1.35 m, and 17.30-26.50 kg, in relation to the other ranges. Nonetheless, no differences were observed among mean mandibular ROM values in the ranges 8 to 12-14 years, 1.36-1.75 m, and 47-85 kg. Thus, it is suggested that weight, height, and age variables be considered when obtaining mandibular ROM values, particularly in children aged 6 to 7 years, measuring 1.15-1.35 m, and weighing between 17.3-46.5 kg.