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CDC Extended BMI-for-Age Growth Chart (2-20 Years)

Calculate your child's BMI percentile using CDC extended reference data. This chart includes the percent-of-95th-percentile metric for classifying severity of obesity in children aged 2-20 years.

BMI = weight (kg) / height (m)² | Extended: % of 95th percentile

How It Works

This calculator uses the CDC extended BMI-for-age reference data for children and adolescents aged 2 to 20 years. Beyond standard BMI percentiles, it calculates the percent-of-95th-percentile metric, which the CDC and the American Academy of Pediatrics recommend for classifying severity of obesity. The standard percentile curves compress at the upper extreme, making it difficult to distinguish moderate from severe obesity. The extended method addresses this by expressing BMI as a percentage of the age- and sex-specific 95th percentile value.

Example Problem

A 10-year-old boy is 140 cm tall and weighs 35 kg. What is his BMI percentile?

  1. Enter the child's date of birth and measurement date (10 years apart).
  2. Select 'Boy' for gender.
  3. Enter 140 cm for height and 35 kg for weight.
  4. BMI = 35 / (1.40)² = 17.9 kg/m².
  5. The calculator finds the LMS parameters for boys at age 10 and computes the percentile.
  6. Result: approximately the 63rd percentile, in the healthy weight range.

Key Concepts

BMI-for-age is the recommended screening tool for overweight and obesity in children over 2. Unlike adult BMI categories, children's BMI interpretation requires age- and sex-specific percentiles because body composition changes as children grow. The percent-of-95th-percentile metric adds granularity above the 95th percentile: 100-119% indicates obesity (Class I), 120-139% indicates severe obesity (Class II), and 140%+ indicates the most severe obesity (Class III).

Applications

  • Screening for overweight and obesity at well-child visits
  • Classifying severity of obesity using percent-of-95th-percentile
  • Monitoring BMI trends during childhood and adolescence
  • Evaluating effectiveness of weight management interventions
  • Research on childhood obesity prevalence and trends

Common Mistakes

  • Using adult BMI categories (e.g., BMI > 30 = obese) for children — children require age-specific percentiles
  • Not measuring height and weight accurately — small errors significantly affect BMI in children
  • Ignoring that BMI does not distinguish between muscle and fat mass
  • Using standard BMI percentiles alone to classify severity of obesity — the percent-of-95th metric is recommended
  • Confusing BMI percentile with BMI value — a BMI of 18 can be healthy or overweight depending on age

Frequently Asked Questions

What is the difference between the standard and extended CDC BMI charts?

Standard CDC BMI charts show percentiles up to the 97th but compress at the upper range, making it hard to distinguish severity of obesity. The extended chart adds the percent-of-95th-percentile metric, which the CDC recommends for classifying obesity severity in children.

What age range does this calculator cover?

This calculator covers children and adolescents aged 2 to 20 years. BMI is not recommended for children under 2 — use weight-for-length instead.

What does “% of 95th percentile” mean?

This metric expresses the child’s BMI as a percentage of the 95th percentile BMI value for their age and sex. It is recommended by the CDC and the American Academy of Pediatrics for classifying severity of obesity. A value of 120% or higher indicates severe obesity.

Should I use metric or imperial units?

You can use either. The calculator converts automatically. For the most accurate BMI, use height and weight measured at the same visit by a healthcare provider.

Reference: CDC Extended BMI-for-Age Percentiles. Centers for Disease Control and Prevention. https://www.cdc.gov/growthcharts/

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