BMI Calculator for Kids
Calculate your child's BMI percentile instantly with our free BMI calculator for kids ages 2-19. Using official CDC growth charts, get immediate results showing BMI value, percentile ranking, and weight category. Our pediatric BMI calculator accounts for age and gender differences, providing accurate assessments for boys and girls at every stage of development.
How to Calculate BMI for Kids?
BMI for children and teens uses the same formula as adults, but results are interpreted using age- and sex-specific percentiles from CDC growth charts:
- Calculate BMI: Weight (kg) ÷ Height (m)² or [Weight (lb) × 703] ÷ Height (in)²
- Find percentile: Compare BMI to CDC growth charts for child's age and sex
- Interpret category: Below 5th = underweight, 5th-85th = healthy, 85th-95th = overweight, 95th+ = obese
BMI-for-Age Percentile
💡 Try These Examples
📊 Understanding Child BMI Categories
Children's weight status is determined by comparing their BMI to other children of the same age and sex using CDC growth charts. Unlike adults who use fixed BMI ranges, children's categories are based on percentiles:
Underweight
May indicate nutritional deficiency. Consult your pediatrician.
Healthy Weight
BMI is within healthy range. Maintain balanced nutrition.
Overweight
May benefit from lifestyle modifications.
Obese
Work with healthcare provider on a healthy plan.
❓ People Also Ask
What is a normal BMI for a 10 year old?
For a 10-year-old, a healthy BMI typically falls between 14.2-19.4 for boys and 14.0-19.9 for girls (5th to 85th percentile). The 50th percentile (average) is about 16.6 for boys and 16.8 for girls. However, BMI should always be interpreted in context with the child's overall health and growth pattern.
How do you calculate BMI for a child?
Calculate BMI using the formula: weight (kg) ÷ height (m)² or [weight (lb) × 703] ÷ height (in)². Then compare the result to CDC growth charts for the child's age and sex to find their percentile. Unlike adults, children's BMI must be interpreted using percentiles because body composition changes with age.
Why is BMI different for children than adults?
Children's body composition changes significantly as they grow, and differs between boys and girls. Adult BMI uses fixed categories (18.5-24.9 is normal), but children's BMI must be compared to age- and sex-specific growth charts because what's healthy for a 5-year-old differs from a 15-year-old.
At what BMI percentile should I be concerned?
Consult your pediatrician if your child's BMI is below the 5th percentile (underweight) or above the 85th percentile (overweight). Above the 95th percentile indicates obesity. However, a single measurement is less important than tracking trends over time—sudden changes warrant attention.
Is BMI accurate for muscular or athletic children?
BMI may overestimate body fat in muscular, athletic children because it cannot distinguish between muscle and fat mass. Very athletic children with significant muscle development may show elevated BMI despite being healthy. Healthcare providers may use additional measures like skinfold thickness or waist circumference.
How often should I check my child's BMI?
BMI is typically measured at annual well-child visits starting at age 2. More frequent monitoring may be recommended if there are concerns about growth patterns, sudden weight changes, or if the child falls outside the healthy range. Tracking trends over time is more valuable than individual measurements.
📈 BMI Percentile Reference Tables
These tables show BMI values at key percentiles for boys and girls at various ages, based on CDC growth chart data:
Boys BMI-for-Age Percentiles
| Age | 5th %ile | 50th %ile | 85th %ile | 95th %ile |
|---|---|---|---|---|
| 2 years | 14.7 | 16.4 | 18.0 | 19.1 |
| 5 years | 13.8 | 15.4 | 16.9 | 18.0 |
| 8 years | 13.7 | 15.8 | 18.2 | 20.0 |
| 10 years | 14.2 | 16.6 | 19.4 | 21.6 |
| 12 years | 15.0 | 17.8 | 21.1 | 23.7 |
| 15 years | 16.5 | 19.9 | 23.6 | 26.5 |
| 18 years | 18.0 | 21.8 | 25.6 | 28.7 |
Girls BMI-for-Age Percentiles
| Age | 5th %ile | 50th %ile | 85th %ile | 95th %ile |
|---|---|---|---|---|
| 2 years | 14.4 | 16.0 | 17.6 | 18.7 |
| 5 years | 13.5 | 15.2 | 16.8 | 18.0 |
| 8 years | 13.5 | 15.8 | 18.3 | 20.2 |
| 10 years | 14.0 | 16.8 | 19.9 | 22.1 |
| 12 years | 14.8 | 18.0 | 21.7 | 24.2 |
| 15 years | 16.2 | 19.9 | 24.0 | 26.9 |
| 18 years | 17.2 | 21.1 | 25.5 | 28.7 |
Source: CDC Growth Charts, 2000
⚠️ Health Risks Associated with Childhood Obesity
Children with obesity (BMI ≥ 95th percentile) face increased risk for several health conditions:
Cardiovascular
High blood pressure, high cholesterol, and increased risk of heart disease in adulthood.
Type 2 Diabetes
Insulin resistance and impaired glucose metabolism, previously rare in children but now increasing.
Joint Problems
Extra weight puts stress on joints and bones, potentially causing pain and mobility issues.
Sleep Apnea
Breathing problems during sleep that can affect rest quality and daytime functioning.
Mental Health
Increased rates of depression, anxiety, and low self-esteem related to weight stigma.
Adult Obesity
Children with obesity are more likely to have obesity as adults, continuing health risks.
💪 Tips for Maintaining a Healthy Weight
🥗 Nutrition
- Offer fruits and vegetables at every meal
- Choose whole grains over refined grains
- Limit sugary drinks—offer water and milk instead
- Practice portion control with age-appropriate servings
- Eat meals together as a family when possible
🏃 Physical Activity
- Aim for at least 60 minutes of activity daily
- Include a mix of aerobic, muscle, and bone-strengthening activities
- Limit screen time to 1-2 hours per day
- Make activity fun—sports, dance, active play
- Be active as a family with walks, bike rides, or games
😴 Sleep & Lifestyle
- Ensure adequate sleep (9-12 hours for ages 6-12)
- Establish consistent bedtime routines
- Model healthy behaviors as parents
- Focus on health, not appearance or weight numbers
- Celebrate non-scale victories and healthy choices
❓ Frequently Asked Questions
A healthy BMI for children falls between the 5th and 85th percentile for their age and sex. Unlike adults, there's no single "healthy BMI number" for children because what's normal changes with age and differs between boys and girls. The CDC growth charts account for these differences by comparing a child's BMI to other children of the same age and sex.
The BMI formula is the same, but interpretation differs. Adults use fixed ranges (18.5-24.9 is normal), but children need age- and sex-specific percentiles because body fat percentage naturally changes during growth. A BMI of 18 might be healthy for a 10-year-old but underweight for an 18-year-old. Percentiles account for normal developmental patterns.
A child is considered obese if their BMI is at or above the 95th percentile for their age and sex. The 85th to 94th percentile is classified as overweight. Severe obesity is defined as BMI ≥ 120% of the 95th percentile, or BMI ≥ 35, whichever is lower. These classifications help healthcare providers identify children who may benefit from intervention.
No, BMI is a screening tool, not a diagnostic tool. A high BMI indicates a child may have excess body fat, but healthcare providers consider additional factors: growth patterns over time, family history, diet and activity levels, physical exam findings, and sometimes lab tests or other measurements. Athletic children may have high BMI from muscle, not excess fat.
This calculator is designed for children and teens ages 2 through 19. For children under 2 years old, healthcare providers use weight-for-length charts instead of BMI. After age 20, adult BMI categories apply (no longer using percentiles). The CDC growth charts this calculator uses are validated for the 2-19 age range.
BMI can fluctuate during puberty due to growth spurts and body composition changes. Some children gain weight before a height spurt, temporarily increasing their BMI. The CDC percentile charts account for typical pubertal changes, but individual variation exists. Track trends over multiple measurements rather than focusing on single values during this period.
First, consult your pediatrician for a comprehensive assessment. Focus on family-wide healthy lifestyle changes rather than "dieting" for the child alone. Increase physical activity, improve food choices, limit screen time, and ensure adequate sleep. For growing children, the goal is often to maintain weight while growing taller, rather than losing weight. Avoid focusing on numbers or appearance—emphasize health and energy instead.
This calculator uses CDC growth chart data and follows AAP (American Academy of Pediatrics) guidelines for pediatric BMI assessment.
Last reviewed and updated: February 15, 2026
📚 Sources & References
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