1. What is BMI?

BMI (Body Mass Index) 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 way to compare body weights across different heights.

3. Importance of BMI Calculation

Details: BMI is a quick screening tool that helps identify potential weight problems in adults. While it doesn't measure body fat directly, research has shown that BMI correlates with direct measures of body fat.

4. Using the Calculator

Tips: Enter weight in kilograms and height in meters. For accurate results, measure weight without heavy clothing and height without shoes. 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), Obese (≥30).

Q2: Is BMI accurate for everyone?
A: BMI may overestimate body fat in athletes and underestimate it in older people who have lost muscle mass.

Q3: How often should I check my BMI?
A: For most adults, checking every few months is sufficient unless you're actively trying to change your weight.

Q4: Should children use this calculator?
A: No, children and teens need age- and sex-specific BMI percentiles rather than adult categories.

Q5: What's a healthy BMI for South African women?
A: The same ranges apply worldwide, though health risks may vary by ethnicity. 18.5-24.9 is generally considered healthy.