One way to determine a healthy weight range is to measure body mass index (BMI). The National Heart, Lung, and Blood Institute explains that BMI is used to measure if a person is overweight or obese.
The Centers for Disease Control and Prevention explain that the formula for BMI is weight in pounds / [height in inches]^2 x 703. For adults 20 years and older, a healthy BMI range is 18.5 to 24.9. For children and teens, the Centers for Disease Control and Prevention measures against growth charts by age and sex. A healthy range for children is considered between the 5th percentile and 85th percentile of these growth charts.