1. What is BMI?

Body Mass Index (BMI) is a simple index of weight-for-height that is commonly used to classify underweight, normal weight, overweight and obesity in adults. It is defined as the weight in kilograms divided by the square of the height in meters (kg/m²).

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: The formula calculates body mass per unit of surface area, providing a standardized measure for comparing individuals of different sizes.

3. Importance of BMI Calculation

Details: BMI is a simple, inexpensive screening tool for weight categories that may lead to health problems. It correlates moderately well with body fat in most people.

4. Using the Calculator

Tips: Enter weight in kilograms, height in meters, and optionally age. All values must be valid (weight > 0, height > 0).

5. Frequently Asked Questions (FAQ)

Q1: What are the standard BMI categories?
A: Underweight (<18.5), Normal weight (18.5-24.9), Overweight (25-29.9), Obesity (≥30).

Q2: Does BMI apply to everyone?
A: BMI may overestimate body fat in athletes/muscular individuals and underestimate it in older people with lost muscle mass.

Q3: How does age affect BMI interpretation?
A: Older adults may have higher BMI thresholds for overweight/obesity due to natural body composition changes.

Q4: What are limitations of BMI?
A: Doesn't distinguish between muscle and fat, doesn't account for fat distribution, and may vary by ethnicity.

Q5: Should children use this calculator?
A: Children need age- and sex-specific BMI percentiles rather than adult categories.