1. What is BMI?

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

Where:

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

For children and teenagers, the BMI result is compared with other children of the same age and sex using growth charts.

3. Importance of BMI Calculation

Details: BMI is a useful screening tool to identify potential weight problems in children and adults. However, it's not a diagnostic tool and should be followed up with further assessment.

4. Using the Calculator

Tips: Enter weight in kg, height in meters. For children (2-18 years), also enter age and gender to get BMI centile. All values must be valid (weight > 0, height > 0).

5. Frequently Asked Questions (FAQ)

Q1: What is a healthy BMI range for adults?
A: For adults, 18.5 to 24.9 is considered healthy weight. Below 18.5 is underweight, 25-29.9 is overweight, and 30+ is obese.

Q2: How is BMI different for children?
A: Children's BMI is compared with growth charts for their age and sex, resulting in a percentile ranking rather than fixed categories.

Q3: When should BMI be measured?
A: BMI can be measured at any time, but for consistency it's best to measure at the same time of day under similar conditions.

Q4: Are there limitations to BMI?
A: BMI doesn't distinguish between muscle and fat, so athletes may have high BMI without excess fat. It also doesn't account for fat distribution.

Q5: What do BMI centiles mean?
A: For children, below 2nd centile is underweight, 2nd-91st is healthy weight, 91st-98th is overweight, and above 98th is obese.