1. What is BMI for Children?

BMI (Body Mass Index) for children is a measure that adjusts for age and sex, as children's body composition varies as they grow. In New Zealand, BMI-for-age percentiles are used to assess weight status in children and teens.

2. How Does the Calculator Work?

The calculator uses the standard BMI formula:

Where:

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

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

3. Importance of BMI Calculation

Details: Regular BMI monitoring helps identify children at risk of underweight, overweight or obesity. In NZ, this is particularly important given childhood obesity rates.

4. Using the Calculator

Tips: Measure weight in light clothing and height without shoes. Use accurate measurements for best results. The calculator is for children aged 2-18 years.

5. Frequently Asked Questions (FAQ)

Q1: How is child BMI different from adult BMI?
A: Children's BMI is interpreted relative to other children of the same age and sex, using percentile charts rather than fixed categories.

Q2: What are the BMI percentile categories in NZ?
A: Generally: Underweight (<5th %ile), Healthy weight (5th-85th %ile), Overweight (85th-95th %ile), Obese (>95th %ile).

Q3: Where can I find NZ growth charts?
A: The NZ Ministry of Health provides growth charts for clinical use, available through health professionals.

Q4: How often should children's BMI be checked?
A: Annual checks are recommended, or more frequently if there are concerns about growth patterns.

Q5: Are there limitations to BMI for children?
A: BMI doesn't distinguish between muscle and fat, and may be less accurate for very athletic children or those with certain medical conditions.