1. What is BMI?

Body Mass Index (BMI) is a measure of body fat based on height and weight that applies to adults and children. 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 standard BMI formula:

Where:

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

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

3. Importance of BMI for Children

Details: BMI-for-age is the recommended measure for screening overweight and obesity in children aged 2-19 years. It helps identify weight problems that may lead to health issues.

4. Using the Calculator

Tips: Enter weight in kilograms, height in meters, age in years (2-19), and select gender. For accurate results, measure height and weight using standardized methods.

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 for children?
A: Underweight (<5th), Healthy weight (5th-<85th), Overweight (85th-<95th), Obese (≥95th percentile).

Q3: Where can I find NZ-specific BMI charts?
A: The New Zealand Ministry of Health provides growth charts that include BMI-for-age percentiles.

Q4: How often should children's BMI be checked?
A: Annual BMI screening is recommended for children aged 2-19 years as part of routine health assessments.

Q5: Are there limitations to BMI for children?
A: BMI doesn't distinguish between fat and muscle mass. Athletic children may have high BMI due to muscle rather than fat.