1. What is BMI for Children?

BMI-for-age is the measure used for children and teens aged 2-19 years because it accounts for normal differences in body fat between boys and girls and differences at various ages. For children, BMI is age- and sex-specific.

2. How the Calculator Works

The calculator uses the standard BMI formula adjusted for age and sex:

Where:

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

Explanation: The result is compared against New Zealand growth charts for girls to determine the appropriate weight category.

3. Importance of BMI for Children

Details: Tracking BMI in children helps identify potential weight problems early. In New Zealand, about 1 in 3 children are overweight or obese, making regular BMI checks important for health monitoring.

4. Using the Calculator

Tips: For accurate results:

• Measure weight in kilograms without heavy clothing
• Measure height in meters without shoes
• Use the child's exact age in years

5. Frequently Asked Questions (FAQ)

Q1: Is BMI accurate for all children?
A: BMI is a good screening tool but may not reflect body fat in very muscular children or those with certain medical conditions.

Q2: What are the BMI percentile ranges?
A: For NZ girls: Underweight (<5th), Healthy weight (5th-85th), Overweight (85th-95th), Obese (>95th).

Q3: How often should I check my child's BMI?
A: The NZ Ministry of Health recommends annual checks for children aged 2+ years.

Q4: What if my child's BMI is high?
A: Consult your GP or practice nurse. They may assess diet, activity levels, and growth patterns.

Q5: Where can I find NZ-specific growth charts?
A: The NZ Ministry of Health website provides gender-specific BMI-for-age growth charts.