1. What is BMI for Children?

BMI-for-age is a screening tool for underweight, healthy weight, overweight, and obesity in children and teens aged 2-19 years. Unlike adults, children's BMI is interpreted relative to others of the same age and sex.

2. How Does the Calculator Work?

The calculator uses the standard BMI formula:

Where:

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

Note: For children, the raw BMI number must be plotted on NZ-specific growth charts to determine the percentile for age and sex.

3. Importance of BMI Calculation for Children

Details: Regular BMI monitoring helps identify potential weight problems in children. In New Zealand, about 1 in 3 children are overweight or obese, making this an important health screening tool.

4. Using the Calculator

Tips:

• Measure height without shoes
• Use current weight with minimal clothing
• For accuracy, measure at the same time of day
• Use metric units (kg and meters)

5. Frequently Asked Questions (FAQ)

Q1: What BMI percentile is considered healthy?
A: For NZ children, 5th-85th percentile is healthy weight, 85th-95th is overweight, and ≥95th is obese. Below 5th may indicate underweight.

Q2: How often should children's BMI be checked?
A: The NZ Ministry of Health recommends annual BMI checks as part of routine well-child visits.

Q3: Where can I find NZ growth charts?
A: NZ growth charts are available from the Ministry of Health website and Well Child Tamariki Ora programme.

Q4: Does BMI work for all ethnicities?
A: While BMI is used for all children, interpretation may vary slightly by ethnicity. Pacific and Māori children may have different body compositions.

Q5: What if my child's BMI seems high?
A: Consult your GP or practice nurse. They'll consider growth patterns, family history, and other factors before making recommendations.