1. What is BMI?

Body Mass Index (BMI) is a simple calculation using a person's height and weight to screen for weight categories that may lead to health problems. It's widely used by the NHS and other health organizations as a simple, quick method to classify weight status.

2. How Does the Calculator Work?

The calculator uses the standard BMI formula:

Where:

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

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 an important screening tool to identify potential weight problems in adults. However, it's not a diagnostic tool - it doesn't directly measure body fat but correlates with direct measures of body fat.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What are the NHS BMI categories?
A: Underweight (BMI < 18.5), Normal weight (18.5-24.9), Overweight (25-29.9), Obese (30+). These may vary slightly for some ethnic groups.

Q2: Is BMI accurate for everyone?
A: BMI may overestimate body fat in athletes and those with muscular builds, 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 lose or gain weight.

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

Q5: What if my BMI is high?
A: Consult your GP who may suggest further tests (like waist measurement) and can provide advice on healthy weight management.