BMI Calculator for Children & Teens
Estimate BMI-for-age category for children and teens ages 2-20 using simplified CDC growth chart percentile cutoffs. BMI in children is age and sex-specific.
Clinical-use note
This calculator gives an educational estimate from simplified CDC BMI-for-age cutoffs. For an exact child BMI percentile, use the official CDC calculator or ask a pediatrician to plot BMI on a growth chart using age in months, sex, height, and weight.
CDC Weight Categories for Children
Underweight (< 5th percentile)
Below healthy range — consult a pediatrician
Healthy Weight (5th – 84th percentile)
Normal, age-appropriate weight
Overweight (85th – 94th percentile)
Above healthy range for age and sex
Obese (≥ 95th percentile)
Well above healthy range — seek medical guidance
Quick Answers for Child and Teen BMI Percentiles
What BMI is overweight for a 10-year-old girl?
In this simplified CDC cutoff table, a 10-year-old girl reaches the overweight range at about BMI 19.9, which corresponds to the 85th percentile cutoff. Exact clinical percentiles should be checked with the CDC calculator or a pediatrician.
Is BMI 19.7 high for a 10-year-old girl?
BMI 19.7 for a 10-year-old girl lands just below the 85th percentile in this simplified table, around the low-80s percentile. That is close to the overweight cutoff, so trend, height measurement accuracy, and clinical context matter.
Do teen BMI calculators use adult BMI ranges?
No. Teens should use BMI-for-age percentiles until age 20 because puberty changes body composition quickly. Adult cutoffs such as 25 and 30 are not the right interpretation for children and teens.
Can I use this calculator for a child under 2?
No. Children under 2 are normally assessed with infant growth standards and pediatric measurements, not this BMI-for-age calculator.
Need the adult version? Use the adult BMI calculator. Building a full family health picture? Compare BMI with daily calorie needs, protein targets, and body fat estimates.
Understanding BMI in Children: A Parent's Complete Guide
Body Mass Index for children and teens is fundamentally different from adult BMI. While adult BMI uses fixed categories (underweight < 18.5, normal 18.5-24.9), children's BMI must be interpreted using age- and sex-specific growth charts because body composition changes dramatically during development. A BMI of 18 may be healthy for one child and a different category for another child depending on age and sex. This calculator estimates the CDC BMI-for-age category from simplified percentile cutoffs.
The CDC reports that approximately 1 in 5 U.S. children and adolescents have obesity, with the 2017 to March 2020 estimate at 19.7% for ages 2-19. BMI is a screening tool, not a diagnosis. It should be interpreted with growth pattern, medical history, physical exam, health behaviors, and clinician judgment. For adults, use our standard BMI calculator.
How CDC Growth Charts Work
The CDC BMI-for-age growth charts compare a child's BMI to reference populations of children of the same age and sex. Percentiles indicate how a child's BMI compares to others. A child at the 75th percentile has a higher BMI than 75% of children their age and sex. The four weight status categories are:
Underweight (< 5th percentile)
May indicate nutritional deficiency, growth delay, or underlying medical condition. The pediatrician will evaluate growth trajectory, dietary intake, and rule out conditions like celiac disease or thyroid disorders.
Healthy Weight (5th–84th percentile)
Appropriate weight for age and height. This broad range accounts for natural diversity in children's body types. Focus on healthy eating habits, sleep, and regular physical activity.
Overweight (85th–94th percentile)
Above the recommended range. Small lifestyle changes can be effective: fewer sugary drinks, more outdoor play, better sleep routines, and higher dietary quality. Avoid restrictive dieting without clinician guidance.
Obese (≥ 95th percentile)
Significantly above the healthy range. Associated with increased risk of type 2 diabetes, high blood pressure, and psychological effects. Professional guidance from a pediatrician or pediatric nutritionist is recommended.
Important: for many children, the clinical goal may be slower weight gain while height catches up, not rapid weight loss. Growing children need sufficient calories and nutrients for development. For adults tracking their own health alongside their children's, use our body fat calculator or ideal weight calculator.
BMI Changes During Normal Development
Children's BMI follows a characteristic pattern called the "adiposity rebound." BMI increases during infancy, then decreases through early childhood (ages 2-5), reaching its lowest point around age 5-6. It then rises through adolescence into adulthood. Children who experience an early adiposity rebound (before age 5) are at higher risk for overweight in later years. This is why tracking BMI trends over time — not just single measurements — is crucial.
Puberty causes significant changes: boys typically gain muscle mass (which increases BMI without excess fat), while girls naturally increase body fat percentage. These developmental changes make the age- and sex-specific percentile approach essential. Your pediatrician will plot your child's BMI on growth charts at each well-child visit to monitor trends. For tracking calorie and nutrition needs during growth, consider using our calorie calculator and protein calculator.
Healthy Habits for Children at Any BMI
- 60 minutes of physical activity daily: The WHO recommends at least 60 minutes of moderate-to-vigorous activity for children aged 5-17. This can include sports, active play, cycling, dancing, or swimming. Use our calories burned calculator to see how different activities compare.
- Reduce long sedentary blocks: Replacing passive screen time with active play, walking, sports, chores, or movement breaks can improve the daily routine without making weight the center of the conversation.
- Family meals matter: Studies show children who eat regular family meals consume more fruits, vegetables, and whole grains, and have lower rates of overweight. Aim for at least 3-4 family dinners per week.
- Adequate sleep: The National Sleep Foundation recommends 9-12 hours for school-aged children (6-13) and 8-10 hours for teens. Poor sleep is linked to increased appetite hormones and weight gain. Adults can use our sleep calculator to optimize their own schedules.
- Avoid using food as reward: Associating food with emotions can lead to unhealthy eating patterns. Praise effort and behavior instead.
Remember that children's health encompasses far more than BMI alone. Physical fitness, mental health, sleep quality, and dietary diversity all contribute to wellbeing. If you're managing a family budget while prioritizing nutrition, tools like salary planning and financial calculators can help with household budgeting.
Official Sources Used
For medical decisions, compare this estimate with official growth chart tools and a qualified clinician. These references explain the BMI-for-age categories, CDC growth chart use, childhood obesity prevalence, and physical activity guidance:
- CDC Child and Teen BMI Calculator
- CDC Child and Teen BMI Categories
- CDC Childhood Obesity Facts
- CDC Growth Chart Training
- WHO Physical Activity Guidance
Frequently Asked Questions
Can a muscular child have a falsely high BMI?▼
Should I put my overweight child on a diet?▼
How often should children's BMI be checked?▼
Are the CDC and WHO growth charts different?▼
Health Disclaimer
This calculator is for informational and educational purposes only. Results are estimates from simplified percentile cutoffs and may not match a clinical growth chart calculation. This tool does not provide medical advice. Always consult a qualified healthcare professional before making health, fitness, or dietary decisions. Individual results may vary based on factors not captured by these calculations.
Frequently Asked Questions
Can a muscular child have a falsely high BMI?
Yes. Athletic children can have a higher BMI because of lean mass, and BMI does not separate fat mass from muscle mass. A pediatrician can interpret BMI with growth history, physical exam, activity level, family history, and other measurements.
Should I put my overweight child on a diet?
Do not start a restrictive weight-loss plan for a growing child without medical guidance. A safer first step is usually better food quality, fewer sugary drinks, more active play, consistent sleep, and family-level habits. A pediatrician can decide whether weight maintenance, slower gain, or a structured treatment plan is appropriate.
How often should children's BMI be checked?
BMI is usually reviewed during well-child visits and interpreted as a trend, not a one-off number. A child crossing percentile lines upward over time deserves more attention than a stable percentile. Children above the 85th percentile may need closer follow-up from a clinician.
Are the CDC and WHO growth charts different?
Yes. The WHO growth charts (used for children under 2 worldwide) describe how children should grow under optimal conditions (breastfed, healthy environments). The CDC growth charts (used in the U.S. for ages 2-20) describe how American children actually grew, based on national survey data. The WHO charts generally produce higher obesity rates because they use a healthier reference population. This calculator uses CDC charts, which are standard practice in the United States.