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Child BMI & Percentile – CDC Growth Chart

Quick answer

This calculator computes BMI for children and teens ages 2–19 and see the CDC percentile: underweight below 5th, healthy 5th–85th, overweight to 95th, obese above.

Figures are estimates from this calculator’s standard formula — adjust the inputs in the tool below for your exact number.

How Child BMI Percentiles Work

BMI = kg ÷ m²; percentile from CDC growth charts by age and sex (2–19 years)

A child’s BMI number means nothing on its own — a BMI of 17 is normal for a 7-year-old girl and underweight for a 15-year-old boy. So pediatric practice plots BMI against CDC growth charts and reports a percentile comparing the child with same-age, same-sex peers. This calculator computes BMI = weight ÷ height², then places it on the age- and sex-specific curve: below the 5th percentile is underweight, 5th–85th is the healthy weight range, 85th–95th is overweight, and above the 95th percentile is obesity. Worked example: a 10-year-old boy weighing 38 kg at 140 cm has BMI 38 ÷ 1.4² = 19.4, which sits near the 75th percentile — healthy. Because children grow, one measurement never earns a diagnosis; pediatricians track the curve across visits.

  1. 1

    Enter the measurements

    Weight in kg and height in cm, plus age and sex

  2. 2

    Get BMI and percentile

    BMI is plotted on the CDC growth chart for that age

  3. 3

    Read the category

    Underweight, healthy, overweight or obese by percentile

Use Cases

Pediatric check-ins

Plot the growth curve between annual well-child visits

Sports participation

Coaches screen weight categories fairly by percentile, not adult BMI

Family awareness

Catch an upward percentile jump before it crosses the 85th line

Tips

  • 1

    Measure height without shoes for accurate percentiles

  • 2

    Growth spurts shift percentiles — watch the trend, not one point

  • 3

    Share results with your pediatrician rather than self-diagnosing

Common Mistakes

  • Applying adult BMI categories to children

  • Using a single measurement to declare a child overweight

  • Putting growing children on aggressive calorie deficits

  • Comparing a child’s BMI number with a sibling of a different age

FAQs

What BMI percentile is healthy for a child?

The healthy range runs from the 5th to the 85th percentile on CDC growth charts for the child’s age and sex.

Why is child BMI percentile-based?

Body composition changes with age and sex, so a fixed BMI number cannot define healthy weight — the percentile compares peers fairly.

When is a child considered obese?

At or above the 95th percentile for age and sex; 85th–95th is the overweight band.

Should I put my child on a diet?

Not without medical advice — the standard approach for ages 2–19 is weight maintenance while height catches up.

How often should BMI be checked?

At each well-child visit, typically yearly; more frequent checks only if the pediatrician tracks a trend.

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