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WHO BMI-for-Age Growth Chart (5-19 Years)

Calculate your child's BMI percentile using WHO Growth Reference 2007 data for ages 5-19 years. BMI-for-age is the recommended screening tool for overweight and obesity in school-age children and adolescents.

BMI = weight (kg) / height (m)² | LMS: Z = ((X/M)^L - 1) / (L x S)

How It Works

This calculator uses the WHO Growth Reference 2007 for BMI-for-age in children and adolescents aged 5 to 19 years. Unlike adult BMI, which uses fixed cutoffs, children's BMI interpretation requires age- and sex-specific percentiles because body composition changes throughout growth. The calculator first computes BMI from height and weight, then uses the LMS method to determine the percentile and Z-score relative to the WHO reference population.

Example Problem

A 12-year-old girl is 152 cm tall and weighs 42 kg. What is her BMI-for-age percentile?

  1. Enter the child's date of birth and measurement date (12 years apart).
  2. Select 'Girl' for gender.
  3. Enter 152 cm for height and 42 kg for weight.
  4. BMI = 42 / (1.52)² = 18.2 kg/m².
  5. The calculator finds the LMS parameters for girls at age 12 and computes the percentile.
  6. Result: approximately the 50th percentile, in the healthy weight range.

Key Concepts

BMI-for-age is the recommended screening tool for overweight and obesity in children over 5. Children’s healthy BMI changes as they grow — a BMI of 18 might be healthy for a 15-year-old but overweight for a 5-year-old. The WHO defines overweight as above the 85th percentile and obesity as above the 97th percentile (corresponding to +1 and +2 Z-scores). BMI does not distinguish between muscle and fat mass, so clinical assessment is always needed alongside the percentile.

Applications

  • Screening for overweight and obesity at school health programs
  • Monitoring BMI trends during childhood and adolescence
  • Evaluating effectiveness of lifestyle interventions
  • International health comparison using WHO reference data
  • Research on childhood obesity prevalence and trends

Common Mistakes

  • Using adult BMI categories (e.g., BMI > 25 = overweight) 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 this chart for children under 5 — WHO weight-for-height is recommended for younger children
  • Confusing BMI percentile with BMI value — the same BMI number means different things at different ages

Frequently Asked Questions

What age range does this BMI calculator cover?

This calculator uses the WHO Growth Reference 2007 for children and adolescents aged 5 to 19 years (60 to 228 months). For younger children, different growth standards should be used, such as our WHO 0-5 year weight-for-age charts.

Why is BMI percentile used instead of just BMI?

Children’s healthy BMI changes as they grow. A BMI of 18 might be healthy for a 15-year-old but overweight for a 5-year-old. Percentiles compare a child to others of the same age and sex, giving a more meaningful assessment.

How is this different from an adult BMI calculator?

Adult BMI calculators use fixed cutoffs (e.g., BMI over 25 = overweight). For children, the same BMI number means different things at different ages. This calculator compares BMI to age- and sex-specific WHO reference data to determine the percentile.

Should I be concerned if my child is above the 85th percentile?

A BMI above the 85th percentile suggests overweight, and above the 97th suggests obesity. However, BMI doesn’t distinguish between muscle and fat. Discuss any concerns with your pediatrician, who can evaluate your child’s overall health and growth pattern.

Reference: WHO Growth Reference 2007. World Health Organization. https://www.who.int/tools/growth-reference-data-for-5to19-years

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