1. What is BMI?

Body Mass Index (BMI) is a measure of body fat based on height and weight that applies to children and adults. 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

Explanation: BMI provides a simple numeric measure of a person's thickness or thinness, allowing health professionals to discuss weight problems objectively with their patients.

3. Understanding BMI Percentiles for Boys

Details: For children and teens, BMI is age- and sex-specific because their body composition varies as they grow. BMI-for-age growth charts show the weight status categories used with children and teens (underweight, healthy weight, overweight, obese).

4. Using the Calculator

Tips: Enter weight in kilograms, height in meters, and optionally age for percentile calculation. All values must be valid (weight > 0, height > 0, age between 2-20 if provided).

5. Frequently Asked Questions (FAQ)

Q1: What do the BMI percentiles mean?
A: For boys: Underweight (<5th %ile), Healthy weight (5th to <85th %ile), Overweight (85th to <95th %ile), Obese (≥95th %ile).

Q2: Why use BMI for children?
A: BMI is the most widely used method to screen for weight problems in children because it's simple, non-invasive, and correlates with body fat.

Q3: When should I be concerned about my child's BMI?
A: If your child's BMI is below the 5th percentile or above the 85th percentile, consult with a healthcare provider.

Q4: Are there limitations to BMI?
A: BMI doesn't distinguish between muscle and fat, so muscular children may have high BMI without excess fat. It's a screening tool, not a diagnostic.

Q5: How often should BMI be checked in children?
A: The American Academy of Pediatrics recommends BMI screening annually from age 2.