1. What is BMI for Children?

BMI (Body Mass Index) for children is a measure that adjusts for age and gender, as children's body composition varies as they grow. In New Zealand, BMI-for-age percentiles are used to assess whether a child has a healthy weight.

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 age- and sex-specific growth charts to determine the percentile.

3. Importance of BMI Calculation for Children

Details: Regular BMI monitoring helps identify potential weight problems in children. In NZ, this is particularly important due to higher rates of childhood obesity compared to many other OECD countries.

4. Using the Calculator

Tips: Enter weight in kilograms, height in meters, age in years (2-18), and select gender. For accurate results, measurements should be taken with minimal clothing and no shoes.

5. Frequently Asked Questions (FAQ)

Q1: What BMI percentile is considered healthy?
A: In NZ, 5th to 85th percentile is generally healthy weight, 85th-95th is overweight, and ≥95th is obese.

Q2: Where can I plot my child's BMI percentile?
A: The NZ Ministry of Health provides growth charts, or you can consult with a Well Child Tamariki Ora provider.

Q3: How often should my child's BMI be checked?
A: Regular checks are part of the Well Child Tamariki Ora programme at key developmental stages.

Q4: Are there limitations to BMI for children?
A: BMI doesn't distinguish between muscle and fat, so athletic children may show higher values. Always consider individual circumstances.

Q5: What should I do if my child's BMI is outside the healthy range?
A: Consult with your GP or practice nurse who can assess overall health and provide appropriate advice or referrals.