According to the Centers for Disease Control and Prevention, 13-year old girls who are 5 feet 6 inches tall should have a BMI of between 15.3 (95 pounds) and 22.6 (140 pounds) to be in the healthy weight range. The 50th percentile (average) of the range is 116.5 pounds.
The Centers for Disease Control and Prevention works to inform Americans about health, safety and security threats, including obesity and diabetes. The agency recommends checking BMI-for-age annually or more often if recommended by the child’s doctor. Because height and weight change with growth, a single BMI-for-age calculation is not enough to evaluate long-term weight status. Tracking growth patterns over time can help ensure that someone is achieving or maintaining a healthy weight.