1. What is BMI?

Body Mass Index (BMI) is a measure of body fat based on height and weight that applies to adult men and women. It provides a simple numeric measure of a person's thickness or thinness.

2. How Does the Calculator Work?

The calculator uses the BMI formula for stone and inches:

Where:

• \( weight \) — Weight in stones (1 stone = 14 pounds)
• \( height \) — Height in inches
• 703 — Conversion factor to make BMI unitless

Explanation: The formula converts stone to pounds (×14) then uses the standard BMI calculation adjusted for imperial units.

3. BMI Categories

Standard BMI Categories:

• Underweight: BMI less than 18.5
• Normal weight: BMI 18.5 to 24.9
• Overweight: BMI 25 to 29.9
• Obese: BMI 30 or greater

4. Using the Calculator

Tips: Enter weight in stones (e.g., 11.5 for 11 stone 7 pounds) and height in inches (e.g., 70 for 5'10"). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why use stone instead of pounds or kg?
A: This calculator is designed for those who prefer using stone, which is commonly used in the UK and Ireland to measure body weight.

Q2: How accurate is BMI?
A: BMI is a useful screening tool but doesn't directly measure body fat. Athletes may have high BMI due to muscle mass, not fat.

Q3: What are the limitations of BMI?
A: Doesn't account for muscle mass, bone density, overall body composition, or racial/ethnic differences.

Q4: Is BMI different for children?
A: Yes, children's BMI is age and sex-specific and is interpreted using percentile charts.

Q5: Should I use this if I'm pregnant?
A: BMI calculations during pregnancy aren't meaningful as weight gain is expected and necessary.