What is a BMI percentile?

A BMI percentile shows how your child's BMI compares to other children of the same age and sex. For example, a percentile of 60 means the child's BMI is higher than 60% of other children the same age and sex.

Why is child BMI different from adult BMI?

Children's body composition changes as they grow, and boys and girls grow differently. Therefore, BMI levels that define being underweight, healthy weight, overweight, or obese depend on the child's age and sex, unlike adult BMI which uses fixed numbers.

Is a high BMI percentile always bad?

Not necessarily. BMI is a screening tool, not a diagnostic of body fatness or health. A child with a high muscle mass might have a high BMI. However, a BMI at or above the 95th percentile is often an indicator of excess body fat and potential health risks. Consult a pediatrician for a full assessment.

How often should I check my child's BMI?

BMI is typically tracked during routine well-child visits with your pediatrician. Checking it once a year is usually sufficient to track growth trends.

Children's BMI Percentile Calculator

Estimate a child's BMI-for-age percentile using age, sex, height, and weight, and see how it compares to typical growth charts. Educational only, not medical advice.

This calculator is for educational purposes only and does not provide medical advice, diagnosis, or treatment recommendations. Always consult with a pediatrician or healthcare professional for concerns about your child's growth or health.

Enter Child's Information

Measurement System

Metric (cm, kg)US (ft/in, lb)

Age (years) *

For children and adolescents 2–20 years old

Additional Months (Optional)

For more precise calculation (e.g., 7 years 3 months = 7 years, 3 months)

Sex at Birth * (Required)

BMI-for-age percentiles are sex-specific and required for accurate calculation

Height (cm) *

Weight (kg) *

Enter the child's age, sex, height, and weight to estimate BMI-for-age percentile.

Understanding Child BMI Percentiles

Body Mass Index (BMI) for children and teens is calculated differently than for adults. While the formula to calculate BMI number is the same (weight / height²), the interpretation depends on age and sex because children's body composition changes as they grow and varies between boys and girls.

Instead of fixed BMI thresholds (like 25.0 for overweight in adults), children's BMI is expressed as a percentile relative to other children of the same sex and age.

What do the percentiles mean?

Underweight: Less than the 5th percentile
Healthy Weight: 5th percentile to less than the 85th percentile
Overweight: 85th percentile to less than the 95th percentile
Obesity: 95th percentile or greater

For example, a child in the 75th percentile has a BMI higher than 75% of children their age and sex, which falls within the healthy weight range.

Why BMI-for-Age?

Children grow at different rates. A 5-year-old boy has a very different "normal" BMI than a 15-year-old boy. The Centers for Disease Control and Prevention (CDC) growth charts are used to determine the corresponding percentile for a child's BMI value.

Important Note: BMI is a screening tool, not a diagnostic tool. It does not measure body fat directly. A child may have a high BMI for their age and sex but to determine if excess fat is a problem, a health care provider would need to perform further assessments.

Frequently Asked Questions

Common questions about child BMI percentiles and growth charts.

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