Pediatric BMI Percentile Calculator Formula
Understand the math behind the pediatric bmi percentile calculator. Each variable explained with a worked example.
Formulas Used
BMI
bmi = (weight_lbs * 703) / (height_inches * height_inches)BMI Prime (vs 85th percentile)
bmi_prime = (weight_lbs * 703) / (height_inches * height_inches) / (14 + age * 0.5)Variables
| Variable | Description | Default |
|---|---|---|
weight_lbs | Weight(lbs) | 70 |
height_inches | Height(inches) | 54 |
age | Age(years) | 10 |
How It Works
Pediatric BMI
For children aged 2-19, BMI is calculated the same as adults but interpreted differently using age- and sex-specific percentile charts.
BMI = (Weight in lbs x 703) / (Height in inches)^2
Weight Status Categories
Note: This calculator computes BMI. For exact percentile, use CDC growth charts with the child's age and sex.
Worked Example
A 10-year-old weighing 70 lbs, 54 inches tall.
- 01BMI = (70 x 703) / (54 x 54)
- 02= 49,210 / 2,916
- 03= 16.9
Frequently Asked Questions
Why is pediatric BMI different from adult BMI?
Children's body fat changes with age and differs between boys and girls. The same BMI value means different things at different ages, so percentile charts are used instead of fixed cutoffs.
What percentile is healthy for a child?
A BMI between the 5th and 84th percentiles is considered healthy weight. The 85th-94th is overweight, and 95th or above is obese.
When should I be concerned about my child's BMI?
Talk to your pediatrician if your child's BMI is below the 5th or above the 85th percentile, or if there is a significant change in BMI percentile over time.
Ready to run the numbers?
Open Pediatric BMI Percentile Calculator