1. What is BMI?

Body Mass Index (BMI) is a measure that uses height and weight to work out if weight is healthy. 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:

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

Note: For children, the raw BMI number is plotted on a gender-specific BMI-for-age growth chart to determine the BMI percentile.

3. Importance of BMI Calculation for Children

Details: BMI-for-age is the recommended measure for screening overweight and obesity in children aged 2-18 years. It helps identify potential weight problems that may lead to health issues.

4. Using the Calculator

Tips: Enter weight in kg, 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: How is child BMI different from adult BMI?
A: Child BMI is interpreted relative to other children of the same age and sex, using percentile rankings rather than fixed categories.

Q2: What are the NHS BMI percentile categories for children?
A: Underweight (<2nd percentile), Healthy weight (2nd-90th percentile), Overweight (91st-97th percentile), Very overweight (>98th percentile).

Q3: When should I be concerned about my child's BMI?
A: Consult a healthcare professional if your child's BMI is below 2nd percentile or above 91st percentile for their age and sex.

Q4: 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.

Q5: Where can I find NHS growth charts?
A: NHS growth charts are available at GP surgeries, child health clinics, and online through official NHS resources.