BMI Calculator for Teens
BMI for Teenagers Is Different
Unlike adults, teen BMI is interpreted using age and gender-specific percentile charts. A BMI of 23 might be perfectly healthy for a 17-year-old boy but could indicate overweight for a 13-year-old girl. This is because teens are still growing, and healthy body fat levels change with age and puberty.
Teen BMI percentile categories:
- Underweight: Below the 5th percentile
- Healthy weight: 5th to 84th percentile
- Overweight: 85th to 94th percentile
- Obese: 95th percentile or above
These percentiles are based on CDC growth charts from 2000. A teen at the 60th percentile has a higher BMI than 60% of teens of the same age and gender.
Calculate BMI
Enter height and weight to get a BMI value. For teens, interpretation requires age-specific percentile charts (see below).
Open BMI Calculator →Note: Adult BMI categories don't apply to teens. Use the percentile chart below to interpret results.
50th Percentile BMI by Age & Gender (Typical/Median)
| Age | Girls (50th %ile) | Boys (50th %ile) | Girls (85th %ile) Overweight threshold | Boys (85th %ile) Overweight threshold |
|---|---|---|---|---|
| 13 | 18.7 | 18.5 | 22.6 | 21.8 |
| 14 | 19.4 | 19.2 | 23.3 | 22.6 |
| 15 | 20.0 | 19.9 | 24.0 | 23.4 |
| 16 | 20.6 | 20.5 | 24.6 | 24.2 |
| 17 | 21.1 | 21.2 | 25.2 | 24.9 |
| 18 | 21.5 | 21.7 | 25.7 | 25.6 |
| 19 | 22.0 | 22.3 | 26.1 | 26.3 |
Data from CDC Growth Charts (2000). 50th percentile = median; 85th percentile = overweight threshold.
Key Considerations for Teens (Ages 13–19)
Why Adult BMI Categories Don't Work for Teens
Adult BMI uses fixed categories (underweight <18.5, normal 18.5–24.9, etc.). For teens, these don't apply because body composition changes rapidly during puberty. A 13-year-old boy with a BMI of 21 is at the 75th percentile, while an 18-year-old with the same BMI is at the 50th percentile. Percentile-based interpretation accounts for these developmental differences.
Puberty & BMI
During puberty, it's normal for BMI to increase. Girls typically gain body fat before their growth spurt, and boys gain lean muscle mass. A temporary increase in BMI percentile during ages 11–14 doesn't necessarily indicate a health problem — it often reflects normal pubertal development. Trends over time are more meaningful than single measurements.
When to Be Concerned
Speak with a pediatrician if your teen's BMI percentile has jumped dramatically (crossing two or more percentile lines), is consistently above the 95th percentile, or is below the 5th percentile. However, BMI alone should never be used to restrict a teenager's food intake or prescribe a "diet." Teens need adequate nutrition for growth and development.
Frequently Asked Questions
For teens, "normal" is defined as the 5th to 84th percentile for their age and gender, not by a single number. For example, a normal BMI for a 15-year-old girl ranges from about 16.0 to 24.0, while for a 15-year-old boy it's about 15.5 to 23.4. Use CDC growth charts to find the exact percentile.
BMI is a reasonable screening tool for teens when using age/gender-specific percentiles, but it has the same limitation as for adults — it doesn't distinguish between muscle and fat. Athletic teens, especially those in sports like football or gymnastics, may have elevated BMI from muscle mass rather than excess fat.
Teens should never diet to lower BMI without medical guidance. Restrictive eating during adolescence can impair growth, delay puberty, weaken bones, and increase risk of eating disorders. If a teen's BMI is in the overweight or obese range, a pediatrician may recommend lifestyle changes focused on more physical activity and healthier food choices rather than calorie restriction.
The American Academy of Pediatrics recommends BMI screening at annual well-child visits. Tracking BMI percentile over time (rather than focusing on single measurements) gives a better picture of growth trajectory. Most electronic health records automatically plot BMI-for-age at each visit.
Sources & References
- CDC. "About Child & Teen BMI." Centers for Disease Control and Prevention, 2024.
- Barlow SE. "Expert Committee Recommendations on the Assessment, Prevention, and Treatment of Child and Adolescent Overweight and Obesity." Pediatrics, 2007.
- Kuczmarski RJ, et al. "2000 CDC Growth Charts for the United States." National Center for Health Statistics, 2002.
- Styne DM, et al. "Pediatric Obesity — Assessment, Treatment, and Prevention." Endocrine Society Clinical Practice Guideline, 2017.
This content is for informational purposes only and does not constitute medical advice. Consult a healthcare provider for personalized recommendations.