For children age 2–12, BMI is plotted as a percentile against the CDC 2000 growth reference cohort for the same age and sex. Underweight is below the 5th percentile, healthy weight is between the 5th and 85th, overweight is 85th to 95th, and obesity is at or above the 95th percentile. Severe obesity is sometimes defined as 120% of the 95th percentile.
Why a single reading is not enough
Children's body composition changes as they grow. The most useful information comes from a trend across multiple measurements, not a single number. Your paediatrician will plot height, weight and BMI on the CDC growth charts and look at the curve over time. This calculator gives you a quick reference band for one reading — useful for curiosity, not for diagnosis.
What the result means
The calculator shows your child's BMI and the CDC reference band (likely underweight, healthy, overweight, or obese) using a coarse threshold table. For an exact percentile (e.g. "62nd percentile"), you need a CDC LMS lookup or your paediatrician's growth chart. If the reading is in the overweight or obese band, schedule a review — a single reading is not a diagnosis, but a trend in that direction is worth investigating.
Next steps
- Child BMI calculator for ages 2–19
- Teen BMI calculator for ages 13–19
- CDC growth charts and reference tables
- Is BMI accurate for kids?