The child’s weight should be considered across months, and a slight drop from one month to the next does not require any attention. Besides, the baby’s weight also depends;upon the genetic constitution of the parents. Children’s weight is usually measured within a range, and not as a hard and fast number.Here is a simple chart that show the estimated weight gain for children according to their age.
Weight gain according to Age
Gain of 175 to 210 g per week from birth to three months

Double the birth weight by ;5 months

Gain of about 400 g of weight every month till one year

Triple the birth weight ;by 1 year

4 times the birth weight by 2 years

5 times the birth weight by 3 years

6 times the birth weight by 5 years

7 times the birth weight by 7 years

10 times the birth weight by 10 years
On average, a child gains 2 kg every year between 3 to 7 years of age and 3 kg per year after that till the pubertal growth spurt begins. Please remember that this is just a generic chart, and your child’s pediatrician is the best person to assess your child’s individual case.