1. What is BMI?

Body Mass Index (BMI) is a value derived from the mass and height of a person. It provides a simple numeric measure of a person's thickness or thinness, allowing health professionals to discuss weight problems objectively with their patients.

2. How Does the Calculator Work?

The calculator uses the BMI formula with stones and pounds conversion:

Where:

• \( weight \) — Weight in stones and pounds (converted to total pounds)
• \( height \) — Height in inches
• 703 — Conversion factor (kg/m² to lbs/in²)

Explanation: The equation first converts stone and pounds to total pounds, then calculates BMI using the standard formula adjusted for imperial units.

3. Importance of BMI Calculation

Details: BMI is widely used as a screening tool to identify possible weight problems in adults. While it doesn't measure body fat directly, research has shown that BMI correlates to direct measures of body fat.

4. Using the Calculator

Tips: Enter weight in stones and pounds (1 stone = 14 pounds), and height in inches. All values must be valid (weight components ≥ 0, height > 0).

5. Frequently Asked Questions (FAQ)

Q1: What is a healthy BMI range?
A: For adults, 18.5-24.9 is considered normal weight, 25-29.9 overweight, and 30+ obese. However, these ranges vary slightly by age and ethnicity.

Q2: Why convert stones and pounds?
A: The UK commonly uses stones and pounds for body weight, while BMI calculations typically use total pounds or kilograms.

Q3: Are there limitations to BMI?
A: BMI doesn't account for muscle mass, bone density, or fat distribution. Athletes may have high BMI due to muscle rather than fat.

Q4: Should children use this calculator?
A: Children's BMI is interpreted differently using age and sex-specific percentile charts, not adult categories.

Q5: What's the metric version of this formula?
A: The metric formula is \( BMI = \frac{weight\ (kg)}{height\ (m)^2} \). 1 stone = 6.35kg, 1 inch = 0.0254m.