Case Example 1: BMI-for-Age

Sam is a 9-year-old boy who has a height of 105.4 cm and weight of 16.9 kg. Open the tabs below to calculate Sam’s BMI and view his BMI percentile on a growth chart.

Name: Sam

Age: 9 years

Sex: boy

Height: 105.4 cm

Weight: 16.9 kg

By-Hand Calculation:
(16.9 kg / 105.4 cm / 105.4 cm) x 10,000 = 15.2


BMI-for-Age Percentile:

You can also use CDC’s BMI Calculator to generate BMI metrics for your patients.

Because Sam’s BMI is below the 97th percentile for his age and sex, Sam’s doctor can plot his BMI on CDC’s BMI-for-Age Growth Chart.

BMI-for-Age Growth Chart
2 to 20 years: Boys body mass index-for-age percentiles

Plot the intersection of age on the x-axis (9 years for this patient) and BMI on the y-axis (15.2 for this patient).

Sam has a BMI of 15.2 kg/m2, placing him at the 28th percentile for age and sex. This means that Sam’s BMI is greater than the BMIs of 28% of 9-year-old boys in the growth chart reference population.

Sam’s BMI falls in the Healthy Weight category, which is defined as BMIs from the 5th percentile up to the 85th percentile for sex and age.

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