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. It provides a reliable indicator of body fatness for most people.

2. How Does the Calculator Work?

The calculator uses the standard BMI formula:

Where:

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

Explanation: The equation divides weight by the square of height to account for the fact that weight increases with the square of height.

3. Importance of BMI Calculation

Details: BMI is a simple, quick screening method for weight categories that may lead to health problems. It's used to identify underweight, normal weight, overweight, and obesity in adults.

4. Using the Calculator

Tips: Enter weight in kilograms and height in meters. For pounds and inches, convert first (1 kg = 2.2 lbs, 1 m = 39.37 inches). All values must be valid (weight > 0, height > 0).

5. Frequently Asked Questions (FAQ)

Q1: What are the NHS BMI categories?
A: Underweight (below 18.5), Normal weight (18.5-24.9), Overweight (25-29.9), Obese (30 and above).

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: What's a healthy BMI range?
A: For most adults, 18.5 to 24.9 is considered healthy.

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

Q5: What if my BMI is high?
A: Consult your GP who may suggest other tests like waist measurement or skinfold thickness.