Pediatric BMI Calculator

Children are growing: body fat, muscle mass, and body composition change with age and sex. Fixed BMI cutoffs like 25 or 30 don't work. Instead, a child's BMI is compared to thousands of children of the same age and sex — that comparison is the CDC percentile.

The percentile shows how many children of the same age and sex have a lower BMI. A value at the 75th percentile means 75% of children of the same age have a lower BMI. The 5th to 84th percentile range is considered healthy weight.

By CDC criteria: 85th to below 95th percentile is overweight, 95th percentile or higher is obesity. Below the 5th percentile is underweight.

Age (2–20 years), sex, height and weight. You can switch between metric (kg, cm) and imperial (lbs, in) units. BMI is calculated instantly and classified into the correct percentile category.

The calculator uses a simplified CDC LMS reference table and the Z-score method by Cole & Green (1992). Results are typically within ±1 percentile of the official CDC table — adequate for a first assessment. For medical decisions, always consult a pediatrician.

A single BMI reading is not a diagnosis — what matters is the trend over multiple measurements. If a child stays below the 5th or above the 95th percentile, parents should consult a pediatrician to review nutrition, activity, and possible medical causes.