Calculating the ideal body weight or BMI for children differs from those used for adults. This is because the amount of body fat changes as children grow up.
The accepted formula for calculating BMI in children is weight divided by the height in metres squared and the result multiplied by 703. Age and gender makes a significant difference in what makes the ideal BMI for children.
In the case of children, the BMI of each child is matched against the percentiles for children of the same sex and age. Children with a BMI between the 85th and 95th percentile are considered overweight. Percentile is a measure that indicates how a child stands in comparison to a group having the same characteristics, such as a similar age and gender. A child whose BMI falls in the 85th percentile means that he/she weighs more than 85 percent of his/her age group.