1. What is BMI?

Body Mass Index (BMI) is a simple calculation using a person's height and weight. The formula is BMI = kg/m² where kg is a person's weight in kilograms and m² is their height in meters squared. 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 (kg)
• \( height \) — Height in meters (m)

Explanation: BMI provides a simple numeric measure of a person's thickness or thinness, allowing health professionals to discuss weight problems more objectively with their patients.

3. Importance of BMI Calculation

Details: BMI is a screening tool that can indicate whether a child is underweight, healthy weight, overweight, or obese. However, it's not a diagnostic tool and should be used alongside other assessments.

4. Using the Calculator

Tips: Enter weight in kilograms and height in meters. For accuracy, measure height without shoes and weight with minimal clothing. All values must be valid (weight > 0, height > 0).

5. Frequently Asked Questions (FAQ)

Q1: Why is BMI used for children?
A: BMI-for-age is the recommended measure for children because it takes into account normal differences in body fat between boys and girls and differences at various ages.

Q2: What are the BMI categories for children?
A: Children's BMI is interpreted using age- and sex-specific percentiles rather than the adult categories. A BMI below the 5th percentile is underweight, 5th to 85th is healthy, 85th to 95th is overweight, and above 95th is obese.

Q3: How often should a child's BMI be checked?
A: The NHS recommends that children's height and weight (and therefore BMI) should be measured annually as part of the National Child Measurement Programme (NCMP) in England.

Q4: Are there limitations to BMI for children?
A: Yes, BMI doesn't distinguish between fat and muscle, so muscular children may have a high BMI without excess fat. It also doesn't account for different body fat distributions.

Q5: Should I be worried if my child's BMI is high?
A: A high BMI should be discussed with a healthcare professional who can consider other factors like growth patterns, family history, and other health indicators.