BMI for kids is grouped into percentiles, with the 5th to 85th percentile being a healthy weight range, according to WebMD. BMI, or body mass index, is different for children than adults, because their body fat changes as they grow. For example, adult BMI is listed in numbers, not percentiles.
Children with a BMI below the 5th percentile are underweight, children with a BMI between the 85th and 95th percentile are overweight, and children with a BMI over the 95th percentile are obese. Children age 2 and older should get BMI screenings, as recommended by the Centers for Disease Control and the American Academy of Pediatrics, according to WebMD.