The healthy weight for a six-year-old girl who is 4 feet 3 ½ inches tall is between 50 ¼ pounds and 63 ¾ pounds, according to the Centers for Disease Control and Prevention. These fall within the healthy body mass index-for-age range for a girl of her age and height.
A child's ideal weight is calculated by dividing her weight by the square of her height and then comparing the number to a standard range of values. This number is called the body mass index, or BMI. The BMI is then compared against a BMI-for-age growth chart that indicates whether a child is underweight, normal, overweight or obese based on standard percentile ranges.