The height of a three-month-old baby is about 75cm and the weight is about 6kg, but there are individual differences. The height of a 3-12 month old baby is about 75cm, and the weight can be estimated according to the formula (age + 9)/2, and the weight of a three-month old baby is about 6kg. However, it should be noted that the growth of children’s height and weight is not equal to the speed of increase, and should be evaluated on the basis of the individual children’s own changes, and should not be evaluated on the basis of the so-called “normal values” as “standards”. The so-called “normal values” should not be taken as the “standard” for evaluation. Due to genetic and environmental factors, there are individual differences in growth and development. Should avoid using the normal value as the basis for evaluation of the baby’s growth and development, evaluation must take into account individual differences, continuous observation and comprehensive understanding, in order to make accurate judgments. If your baby’s height and weight are significantly different from those of children of the same age and gender, it is recommended that you consult a doctor promptly.