The approximate formula for calculating children’s weight is: at birth, the average weight is 3.25Kg; at 3-12 months of age, the average weight is: [age (months) + 9]/2; at 1-6 years of age, the average weight is: age (years) * 2 + 8; at 7-12 years of age, the average weight is: [age (years) * 7-5]/2, all the results are calculated in kg as the counting unit. These calculation formulas belong to the daily estimation method. Due to the different environment and conditions in which each child grows and develops, such as individual differences, feeding methods, genetic factors, and many other influences, the weight will fluctuate up and down to a certain extent around the average value. It is usually necessary to refer to the child’s growth chart to determine whether the approximate range of the child’s weight is normal according to the percentile method, and if there is a significant deviation, it is necessary to ask the pediatric weight care doctor to evaluate the growth level.