Pediatric BMI Calculator

BMI Percentile Categories for Children

For children and teens aged 2 through 19, BMI is not interpreted using the same fixed cutoffs that apply to adults. Instead, a child's BMI is plotted on age-specific and sex-specific growth charts developed by the Centers for Disease Control and Prevention (CDC). The resulting percentile indicates how a child's BMI compares to other children of the same age and sex in the reference population. Below is a detailed breakdown of each weight status category.

It is important to understand that these categories serve as screening tools, not diagnostic criteria. A pediatrician considers the full clinical picture, including the child's growth trajectory over time, family history, physical maturity, diet, activity level, and overall health before drawing conclusions about a child's weight status. For a deeper understanding of how percentiles work, see our BMI percentile calculator guide.

Average BMI by Age and Sex (50th Percentile)

The table below shows the approximate 50th percentile BMI values for boys and girls at each age from 2 through 19, based on CDC growth chart data. The 50th percentile represents the median: half of children that age and sex have a BMI below this value, and half have a BMI above it. Notice how average BMI changes substantially across childhood and adolescence, which is precisely why fixed adult BMI cutoffs cannot be used for children.

Source: Approximate values derived from CDC Clinical Growth Charts, 2000 (revised). These are median (50th percentile) values and represent population averages. Individual healthy BMI can vary significantly. For the full data tables, see the CDC growth charts.

Several important patterns emerge from this data. First, BMI naturally decreases from age 2 to around ages 4-6, a phenomenon called adiposity rebound. This is normal and reflects the fact that toddlers naturally shed baby fat during early childhood. After the adiposity rebound, BMI gradually increases through the rest of childhood and adolescence. Second, boys and girls track similarly until around age 14, after which boys tend to have slightly higher median BMI values than girls. This divergence reflects differences in puberty timing and body composition changes. To learn more about how age factors into BMI interpretation for all ages, visit our BMI calculator by age and read our guide on BMI by age.

Why Children Use Percentiles Instead of Fixed Cutoffs

If you have used a standard BMI calculator for adults, you know that the categories are straightforward: a BMI under 18.5 is underweight, 18.5 to 24.9 is normal, 25 to 29.9 is overweight, and 30 or above is obese. These fixed numbers work reasonably well for adults because their bodies have finished developing. For children and adolescents, however, fixed cutoffs are meaningless. Here is why pediatric BMI requires age-specific and sex-specific percentiles.

Body Fat Changes Naturally as Children Grow

Children's body composition is in constant flux. Infants and toddlers carry a relatively high percentage of body fat, which is normal and necessary for brain development and energy reserves. Between ages 2 and 6, children naturally become leaner as they grow taller and more physically active. After the adiposity rebound (typically around ages 5-7), body fat gradually increases again through adolescence. A BMI of 16 might be perfectly normal for a 4-year-old but would be severely underweight for a 16-year-old. Fixed cutoffs simply cannot account for these natural developmental changes.

Boys and Girls Develop at Different Rates

Puberty transforms body composition dramatically, and it happens at different ages and rates for boys and girls. Girls typically enter puberty between ages 8 and 13 and naturally accumulate more body fat in their hips, thighs, and breasts. Boys typically enter puberty between ages 9 and 14 and tend to gain more muscle mass relative to fat. These differences mean that a "healthy" BMI number looks different for a 13-year-old girl than a 13-year-old boy, even if they are the same height. Sex-specific percentile charts account for this by comparing each child only to other children of the same sex. For more on how BMI interpretation differs between sexes, see our women's BMI calculator and men's BMI calculator.

Growth Spurts Cause Temporary BMI Changes

Children do not grow at a steady, uniform rate. Instead, they experience growth spurts during which they may gain height rapidly, gain weight rapidly, or both, often not simultaneously. A child who is about to have a height growth spurt may temporarily appear "overweight" because they have gained weight in preparation for growing taller. Conversely, a child in the middle of a height spurt may appear lean because they have stretched upward without gaining proportional weight. Percentile charts smooth out these fluctuations when a child's BMI is tracked over time, allowing pediatricians to identify genuine trends rather than reacting to temporary changes.

What Is Normal at Age 5 Is Very Different from Age 15

Consider this: the 50th percentile BMI for a 5-year-old boy is approximately 15.5. For a 15-year-old boy, the 50th percentile BMI is approximately 20.5. If you applied the adult BMI scale to the 5-year-old, a BMI of 15.5 would classify that child as severely underweight. And if you used a child's standard for the teenager, a BMI of 20.5 might look high. The percentile system resolves this problem by always comparing a child to the appropriate reference group, ensuring that the interpretation is age-appropriate.

The CDC developed its growth charts using data from national health surveys conducted between 1963 and 1994. These charts represent the growth patterns of a large, representative sample of American children before obesity rates rose sharply. You can access and download the full charts directly from the CDC growth charts page.

Understanding Growth Charts

Growth charts are the primary tool pediatricians use to monitor a child's physical development. While this calculator gives you a single percentile snapshot, understanding how growth charts work will help you have more productive conversations with your child's doctor.

How to Read a Growth Chart

A growth chart plots a child's measurement (such as BMI, weight, height, or head circumference) against their age. The chart contains several curved lines, each representing a specific percentile (typically the 5th, 10th, 25th, 50th, 75th, 90th, and 95th). When your pediatrician plots your child's BMI on the chart, the point where it falls relative to these curves tells you what percentage of same-age, same-sex children have a lower BMI. For example, a child at the 70th percentile has a BMI higher than 70% of children their age and sex and lower than 30%.

What Percentiles Really Mean

A common misunderstanding is that higher percentiles are always better or that the 50th percentile is a "target." Neither is true. The 50th percentile simply represents the statistical median. A child at the 25th percentile is not "below average" in a concerning way; they are simply on the smaller side of normal. Similarly, a child at the 75th percentile is not "above average" in a worrying way; they are on the larger side of normal. The entire range from the 5th to the 84th percentile is considered healthy for BMI, which aligns with the healthy BMI range concept used in different ways for adults. What matters most is not where a child falls at any single point in time, but how their percentile tracks over time.

Tracking Over Time Is What Matters Most

The most valuable information from growth charts comes from plotting multiple measurements over months and years. A child who has consistently tracked along the 30th percentile since age 2 is following a normal, expected growth pattern, even though their BMI is below the median. Conversely, a child who was at the 50th percentile at age 6 but has climbed to the 85th percentile by age 9 is showing a trend that warrants investigation, even though they are not yet classified as obese. Pediatricians call this "crossing percentile lines," and it can signal changes in diet, activity, or underlying health conditions. This is why regular well-child visits are so important. For related reading on how BMI tracking works in practice, check out our BMI tracking guide.

Different Charts for Different Purposes

The CDC publishes several types of growth charts. BMI-for-age charts are used for children aged 2-19. For children under 2, the World Health Organization (WHO) growth standards are preferred, which use weight-for-length instead of BMI. The WHO child growth standards are based on data from children in multiple countries who were raised in optimal health conditions (breastfed, non-smoking environments, etc.) and are considered the gold standard for infants and toddlers.

Childhood Obesity: Facts and Prevention

Childhood obesity is one of the most significant public health challenges worldwide. Understanding the scope of the problem, its health consequences, and evidence-based prevention strategies is essential for parents and caregivers.

Current Statistics

According to CDC data on childhood obesity, the prevalence of obesity among children and adolescents in the United States has more than tripled since the 1970s. Key statistics include:

• Approximately 19.7% of children and adolescents aged 2-19 are affected by obesity in the United States, representing roughly 14.7 million young people.
• Obesity rates are highest among adolescents aged 12-19 (22.2%), followed by children aged 6-11 (20.7%) and children aged 2-5 (12.7%).
• Severe obesity (BMI at or above 120% of the 95th percentile) affects approximately 6.7% of children and adolescents.
• Globally, the World Health Organization reports that the number of overweight children under age 5 was estimated at 37 million in 2022, and over 390 million children and adolescents aged 5-19 were overweight.

Health Risks of Childhood Obesity

Childhood obesity is not merely a cosmetic concern. It carries serious, well-documented health risks that can begin in childhood and persist into adulthood. Understanding the BMI categories helps parents identify when intervention may be needed:

• Type 2 diabetes: Once considered an adult-only disease, type 2 diabetes is now diagnosed in children with obesity at increasing rates. Insulin resistance often begins in childhood.
• Cardiovascular disease risk factors: Children with obesity frequently have elevated blood pressure, high cholesterol, and abnormal lipid profiles, all of which increase the risk of heart disease later in life.
• Asthma and breathing problems: Obesity increases the risk and severity of asthma and can cause sleep apnea, a condition where breathing repeatedly stops during sleep.
• Joint and musculoskeletal problems: Excess weight places additional stress on growing bones and joints, increasing the risk of fractures, flat feet, and conditions like Blount's disease and slipped capital femoral epiphysis.
• Fatty liver disease: Non-alcoholic fatty liver disease (NAFLD) is increasingly common in children with obesity and can lead to liver damage over time.
• Mental health effects: Children with obesity are at higher risk for depression, anxiety, low self-esteem, body image issues, and social isolation. Bullying related to weight is common and can have lasting psychological impact.
• Adult obesity: Children with obesity are significantly more likely to become adults with obesity, perpetuating the cycle of associated health risks including heart disease, stroke, certain cancers, and reduced life expectancy.

Risk Factors

Childhood obesity results from a combination of factors, rarely a single cause. Understanding these risk factors helps in developing effective prevention and intervention strategies:

• Dietary patterns: Regular consumption of high-calorie, low-nutrient foods and beverages, including fast food, sugary drinks, and oversized portions.
• Physical inactivity: Sedentary lifestyles including excessive screen time (television, video games, smartphones) and insufficient active play.
• Genetics and family history: Children with parents who have obesity are at higher genetic risk. However, genetics alone do not determine a child's weight; environment and behavior play crucial roles.
• Socioeconomic factors: Limited access to affordable healthy foods, lack of safe spaces for outdoor play, and neighborhoods without sidewalks or parks contribute to higher obesity rates in lower-income communities.
• Psychological factors: Stress, emotional eating, and insufficient sleep can all contribute to weight gain in children.
• Medications: Certain medications, including some antidepressants, anti-seizure medications, and corticosteroids, can promote weight gain.

Prevention Strategies

The good news is that childhood obesity is largely preventable. Research consistently shows that early intervention and family-based approaches are most effective. For practical tips, see our healthy weight tips guide:

• Start healthy habits early: The foundations of healthy eating and active living are best established in early childhood, long before weight problems develop.
• Make it a family affair: Children are far more likely to adopt healthy behaviors when the whole family participates. Avoid singling out one child for dietary restrictions.
• Focus on health, not weight: Emphasize feeling strong, having energy, and being able to do fun activities rather than numbers on a scale. This promotes a healthy relationship with food and body image.
• Create a supportive environment: Keep healthy foods readily available, limit junk food in the home, make physical activity convenient and enjoyable, and model healthy behaviors as a parent.
• Advocate for change: Support school wellness programs, improved school lunch standards, safe playgrounds, and community health initiatives.

For comprehensive evidence-based resources, visit the Mayo Clinic's childhood obesity page and the CDC childhood obesity facts page. For general information on BMI categories and health risks, see our BMI and health risks article and our BMI categories explained guide.

When to Be Concerned

While regular pediatric checkups are the best way to monitor your child's growth, there are certain situations where you should raise the topic with your child's doctor sooner rather than waiting for the next scheduled visit.

Red Flags to Watch For

• Rapid weight gain: If your child gains weight noticeably faster than they are growing in height, or if their clothes sizes are increasing much more quickly than expected for their age.
• Crossing percentile lines: If your child's BMI percentile has jumped significantly upward or downward over the past 6-12 months. A shift of more than one or two major percentile lines (for example, from the 50th to the 85th) is worth discussing.
• Persistent underweight: If your child consistently falls below the 5th percentile and is not growing along an expected curve, especially if they were previously at a higher percentile. Learn more about the implications in our underweight BMI risks article.
• Signs of disordered eating: Hiding food, eating in secret, extreme food restriction, preoccupation with weight or body shape, or a sudden change in eating habits.
• Physical symptoms: Excessive snoring or pauses in breathing during sleep (possible sleep apnea), frequent joint pain, difficulty keeping up with peers during physical activity, or dark velvety patches on the skin (acanthosis nigricans, which can indicate insulin resistance).
• Emotional and social changes: Withdrawing from social activities, being bullied about weight, expressing significant dissatisfaction with their body, or showing signs of depression or anxiety.
• Early puberty signs: In girls, breast development before age 8 or menstruation before age 10. In boys, testicular enlargement before age 9. Obesity is linked to earlier puberty onset.

When to Consult a Pediatrician

You should contact your child's pediatrician if any of the red flags above apply, but also consider scheduling an appointment specifically to discuss weight and growth if:

• Your child's BMI consistently falls in the overweight or obese percentile range (85th percentile or above). Our pediatric BMI calculator guide explains what these thresholds mean.
• You are concerned about your child's eating habits, portion sizes, or food preferences.
• Your child is significantly less active than their peers or resists physical activity.
• There is a strong family history of obesity, type 2 diabetes, heart disease, or other weight-related conditions.
• Your child has been prescribed a medication known to cause weight gain.
• You want guidance on how to talk to your child about weight in a healthy, supportive way.

What Doctors Look For

When evaluating a child's weight, pediatricians do far more than calculate a single BMI number. A comprehensive evaluation typically includes:

• Growth history review: Examining the child's entire growth chart history, not just the current measurement, to identify trends and trajectory changes.
• Dietary assessment: Asking about typical meals, snacks, portion sizes, beverage choices (especially sugary drinks), eating speed, and mealtime environment.
• Activity assessment: Evaluating how much physical activity the child gets daily, what types of activities they enjoy, and how much time they spend sedentary or on screens.
• Family history: Noting whether parents, siblings, or other family members have obesity, diabetes, heart disease, or metabolic conditions.
• Physical examination: Checking blood pressure, looking for physical signs of metabolic problems (like acanthosis nigricans), assessing pubertal development, and evaluating joint health.
• Lab tests (when indicated): Blood tests for glucose levels, insulin, cholesterol, triglycerides, liver function, and thyroid function may be ordered for children in the overweight or obese range.
• Psychosocial screening: Assessing the child's self-esteem, body image, social functioning, and any emotional difficulties related to weight.

For more on what factors affect BMI accuracy, read our articles on BMI accuracy and BMI limitations.

Healthy Habits for Children: A Guide for Parents

Whether your child's BMI is in the healthy range and you want to maintain it, or you are working to improve their health, these evidence-based strategies can help. The American Academy of Pediatrics (AAP) provides comprehensive guidance for parents, and the recommendations below reflect current pediatric best practices.

Nutrition Guidance

Healthy eating habits established in childhood tend to carry into adulthood. Focus on building a positive relationship with food rather than restricting or labeling foods as "good" or "bad." For comprehensive guidance on maintaining a healthy weight at any age, see our healthy weight tips article.

• Prioritize whole foods: Fruits, vegetables, whole grains, lean proteins, and low-fat dairy should form the foundation of your child's diet. Aim for variety and color at every meal.
• Limit sugary beverages: Soda, fruit juice, sports drinks, and sweetened teas are major sources of empty calories for children. Water and plain milk are the best choices. The AAP recommends no more than 4 oz of 100% fruit juice per day for children ages 1-3, and no more than 4-6 oz for ages 4-6.
• Practice portion awareness: Children's portions should be smaller than adult portions. Use age-appropriate plates and bowls, and teach children to listen to their hunger and fullness cues rather than cleaning their plate.
• Eat together as a family: Regular family meals are associated with better nutrition, healthier weight, and improved academic performance. Try to eat together at a table without screens at least several times per week.
• Involve children in food preparation: Kids who help plan, shop for, and prepare meals are more likely to eat the food and develop positive attitudes toward healthy eating.
• Do not use food as reward or punishment: Using dessert as a reward for eating vegetables teaches children to value sweets more and vegetables less. Instead, offer a variety of foods neutrally.

Physical Activity Recommendations

The CDC recommends that children and adolescents aged 6-17 get at least 60 minutes of moderate-to-vigorous physical activity every day. For children aged 3-5, the goal is being physically active throughout the day (at least 3 hours of activity of any intensity). This may sound like a lot, but it can be broken into shorter sessions throughout the day.

• Aerobic activity: Most of the 60 minutes should be moderate-to-vigorous aerobic activity such as brisk walking, running, bicycling, swimming, or active games. Vigorous activity should be included at least 3 days per week.
• Muscle-strengthening: Activities like climbing, push-ups, gymnastics, or playing on playground equipment should be included at least 3 days per week.
• Bone-strengthening: Jumping, running, skipping rope, and sports like basketball or tennis should be included at least 3 days per week.
• Make it fun: The best activity is one your child actually enjoys. Experiment with different sports, dance, martial arts, hiking, swimming, or simply active play with friends.
• Be a role model: Children whose parents are physically active are far more likely to be active themselves. Go for family walks, bike rides, or play in the park together.

Screen Time Limits

Excessive screen time is strongly associated with childhood obesity due to its sedentary nature and the increase in snacking and exposure to food advertising that often accompanies it. The AAP recommends:

• Under 18 months: Avoid screen media other than video chatting.
• 18-24 months: If parents choose to introduce media, select high-quality programming and watch with the child.
• Ages 2-5: Limit screen time to one hour per day of high-quality programming.
• Ages 6 and older: Establish consistent limits on the time spent using media and the types of media. Ensure it does not interfere with sleep, physical activity, and other healthy behaviors.
• Screen-free zones: Keep bedrooms, mealtimes, and family activities screen-free.

Sleep Recommendations

Insufficient sleep is an often-overlooked contributor to childhood obesity. Sleep deprivation disrupts hormones that regulate appetite (increasing ghrelin and decreasing leptin), reduces impulse control, and decreases energy for physical activity. The American Academy of Sleep Medicine recommends:

• Ages 3-5: 10-13 hours per 24 hours (including naps)
• Ages 6-12: 9-12 hours per 24 hours
• Ages 13-18: 8-10 hours per 24 hours

Establishing a consistent bedtime routine, removing screens from the bedroom, and keeping a regular sleep schedule (even on weekends) are the most effective strategies for ensuring adequate sleep.

For more practical guidance on maintaining a healthy weight, see our guides on healthy weight tips and improving your BMI. To understand how weight relates to body composition, visit our lean body mass calculator and read about body fat vs. BMI. Parents interested in ongoing monitoring should read our BMI tracking guide for best practices.

Frequently Asked Questions

Trusted External Resources

The following authoritative sources provide in-depth information about child growth, pediatric BMI, and childhood obesity prevention. We recommend these resources for parents, caregivers, and healthcare professionals seeking detailed, evidence-based guidance.

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