1. What is BMI?

Body Mass Index (BMI) is a person's weight in kilograms divided by the square of height in meters. For children and teens, BMI is age- and sex-specific and is often referred to as BMI-for-age.

2. How is BMI Calculated?

The calculator uses the standard BMI formula:

Where:

• \( weight \) — Body weight in kilograms
• \( height \) — Height in meters

3. Understanding BMI Percentiles

For children and teens: BMI is plotted on CDC growth charts to determine the corresponding BMI-for-age percentile.

Percentile ranges:

• Underweight: < 5th percentile
• Healthy weight: 5th to < 85th percentile
• Overweight: 85th to < 95th percentile
• Obese: ≥ 95th percentile

4. Using the Calculator

Tips: Enter weight in kilograms, height in meters, age in years (2+), and select gender. For accurate results, use precise measurements.

5. Frequently Asked Questions (FAQ)

Q1: Why use BMI-for-age percentiles for children?
A: Because children's body composition varies as they grow, percentiles account for normal differences by age and sex.

Q2: Is BMI accurate for athletes?
A: BMI may overestimate body fat in muscular athletes. Additional assessments may be needed.

Q3: How often should BMI be calculated for children?
A: The AAP recommends BMI calculation at least annually as part of routine health supervision.

Q4: Where can I find CDC growth charts?
A: CDC growth charts are available at https://www.cdc.gov/growthcharts/

Q5: What's the difference between adult and child BMI interpretation?
A: Adults use fixed BMI categories, while children use percentiles relative to peers of same age/sex.