1. What is BMI?

Body Mass Index (BMI) is a simple calculation using a person's height and weight to estimate body fat. It provides a numeric value that helps categorize weight status.

2. How BMI is Calculated

The manual calculation formula for BMI (using pounds and inches) is:

Where:

• \( weight \) — Body weight in pounds (lbs)
• \( height \) — Height in inches (in)
• 703 — Conversion factor to adjust units

Explanation: The formula divides weight by the square of height to account for the relationship between body size and mass.

3. BMI Categories

Standard BMI Categories:

• Underweight: BMI < 18.5
• Normal weight: BMI 18.5-24.9
• Overweight: BMI 25-29.9
• Obese: BMI ≥ 30

4. Using the Calculator

Tips: Enter weight in pounds and height in inches. For accuracy, measure height without shoes and weight with minimal clothing.

5. Frequently Asked Questions (FAQ)

Q1: Is BMI accurate for everyone?
A: BMI is a screening tool but doesn't directly measure body fat. It may overestimate body fat in athletes and underestimate in older adults with muscle loss.

Q2: What's the metric formula for BMI?
A: For kg and meters: BMI = weight(kg) / height²(m). No conversion factor needed.

Q3: Why multiply by 703 in the imperial formula?
A: 703 converts the units from (lbs/in²) to the standard kg/m² scale (1 kg/m² = 703 lbs/in²).

Q4: Should children use the same BMI categories?
A: No, children use age- and sex-specific percentiles rather than fixed categories.

Q5: What are alternatives to BMI?
A: Waist circumference, waist-to-hip ratio, or body fat percentage measurements may provide additional information.