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.

2. How Does the Calculator Work?

The calculator uses the BMI formula:

The calculator converts:

• 1 stone = 6.35029 kg
• 1 pound = 0.453592 kg
• 1 foot = 0.3048 meters
• 1 inch = 0.0254 meters
• 100 cm = 1 meter

3. BMI Categories

Classification:

• Underweight: BMI < 18.5
• Normal weight: BMI 18.5-24.9
• Overweight: BMI 25-29.9
• Obesity Class I: BMI 30-34.9
• Obesity Class II: BMI 35-39.9
• Obesity Class III: BMI ≥ 40

4. Using the Calculator

Tips: Enter either stone and pounds OR kg for weight. Enter either feet and inches OR cm for height. All values must be valid positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Is BMI accurate for everyone?
A: BMI may not be accurate for athletes (high muscle mass), pregnant women, or the elderly (muscle loss).

Q2: What's better than BMI?
A: Waist-to-height ratio or body fat percentage measurements may be more accurate for some individuals.

Q3: Should children use this calculator?
A: No, children and teens need age- and sex-specific BMI percentile calculators.

Q4: How often should I check my BMI?
A: For most adults, checking every few months is sufficient unless actively trying to change weight.

Q5: What's a healthy BMI for older adults?
A: Some research suggests BMI 25-27 may be optimal for older adults rather than the standard 18.5-24.9.