1. What is BMI?

BMI (Body Mass Index) is a measure that uses height and weight to work out if a person's weight is healthy. For children and teens, BMI is age- and sex-specific and is often referred to as BMI-for-age.

2. How Does the Calculator Work?

The calculator uses the BMI formula:

Where:

• \( weight \) — Weight in kilograms (kg)
• \( height \) — Height in meters (m)

Note: For children, the BMI number is plotted on growth charts to determine the BMI-for-age percentile.

3. Importance of BMI Calculation for Children

Details: BMI-for-age is the recommended indicator for screening overweight and obesity in children and teens. It accounts for normal differences in body fat between boys and girls and differences in body fat at various ages.

4. Using the Calculator

Tips: Enter weight in kg, height in meters, age in years (2-18), and select gender. All values must be valid (weight > 0, height > 0, age between 2-18).

5. Frequently Asked Questions (FAQ)

Q1: How is BMI interpreted for children?
A: BMI-for-age is plotted on growth charts to determine a percentile ranking. Underweight (<5th), healthy weight (5th-85th), overweight (85th-95th), obese (≥95th).

Q2: Why is BMI different for children than adults?
A: Children's body composition varies by age and sex, so BMI must be compared against growth charts specific to their age and gender.

Q3: When should BMI be measured in children?
A: The NHS recommends measuring BMI annually from age 2 as part of routine growth monitoring.

Q4: Are there limitations to BMI for children?
A: BMI doesn't distinguish between fat and muscle mass. Very muscular children may have high BMI without excess fat.

Q5: What should I do if my child's BMI is high?
A: Consult your GP or health visitor for assessment. They may consider other factors like growth patterns and family history.