Kids BMI Calculator (BMI for Children and Teens)
This kids BMI calculator estimates Body Mass Index (BMI) for children and teens using weight and height. In children and adolescents, BMI is interpreted using age- and sex-specific growth charts, not the adult BMI categories. Only your child’s healthcare provider can interpret BMI correctly in the context of overall health.
Calculate BMI for a child or teen
Enter your child’s age, sex, weight and height. This tool will calculate BMI and explain how BMI is used together with growth charts. It does not diagnose underweight or overweight.
How is BMI used for children and teens?
In children and adolescents, BMI is only a starting point. The BMI number is plotted on a BMI-for-age growth chart for boys or girls. This shows which percentile your child’s BMI falls into compared with other children of the same age and sex.
- Underweight: BMI-for-age below a certain percentile
- Healthy weight: BMI-for-age in a middle range of percentiles
- Overweight or obesity: BMI-for-age in higher percentile ranges
Exact cut-offs can differ slightly depending on which growth charts are used and local clinical guidelines. That is why BMI in children should always be interpreted by a clinician who knows your child’s full health history, growth pattern and family background.
A single BMI measurement rarely tells the whole story. Your provider will look at how your child has been growing over time, eating patterns, physical activity, sleep, emotional wellbeing and any medical conditions.
Kids BMI Calculator – Frequently Asked Questions
How is kids’ BMI different from adult BMI?
For adults, BMI is interpreted using fixed cut-offs (underweight, normal weight, overweight, obesity). For children and teens, BMI must be compared with other children of the same age and sex using growth charts. This shows BMI percentiles rather than fixed categories.
Can this calculator tell me if my child is overweight?
No. This tool only calculates BMI and provides general information. It does not assign percentiles or make a diagnosis. Only your child’s healthcare provider can interpret BMI correctly and decide whether there is a concern.
Which age range is this calculator for?
This calculator is designed for children and teens roughly between 2 and 19 years of age. For babies and toddlers under 2, weight-for-length charts and other measurements are used instead of BMI.
What should I do if I am worried about my child’s weight?
If you are concerned that your child may be underweight or have excess weight, talk to your doctor, pediatrician or nurse. They can review growth charts, examine your child and discuss healthy eating, physical activity and any other factors that may be important.
Should I put my child on a diet based on an online calculator?
No. Restrictive diets can be harmful for growing children and teens. Any changes to food or activity should be guided by a qualified health professional who can support the whole family in creating a healthy environment.
