1. What is BMI?

Body Mass Index (BMI) is a measure that uses height and weight to work out if a person's 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:

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

Note: For children, the BMI number needs to be plotted on gender-specific growth charts 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 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: 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 growth charts rather than fixed categories.

Q2: What do the BMI percentiles mean?
A: Underweight (<5th percentile), Healthy weight (5th to <85th), Overweight (85th to <95th), Obese (≥95th percentile).

Q3: When should I be concerned about my child's BMI?
A: Consult a healthcare provider if your child is below 5th percentile or above 85th 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 from your GP or health visitor, or on the NHS Choices website.