1. What is BMI?

Body Mass Index (BMI) is a person's weight in kilograms divided by the square of height in meters. For US customary units, we use pounds and inches with a conversion factor of 703. BMI provides a simple numeric measure of a person's thickness or thinness.

2. How Does the Calculator Work?

The calculator uses the US BMI formula:

Where:

• \( weight \) — Weight in pounds (lb)
• \( height \) — Height in inches (in)
• \( 703 \) — Conversion factor (kg/m²)/(lb/in²)

Explanation: The formula converts weight in pounds and height in inches to the standard BMI metric (kg/m²) using the conversion factor 703.

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
• Obesity: BMI 30 or greater

4. Using the Calculator

Tips: Enter weight in pounds and height in inches. For height, you can convert feet to inches (1 foot = 12 inches). For example, 5'7" would be entered as 67 inches.

5. Frequently Asked Questions (FAQ)

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

Q2: What's a healthy BMI range?
A: For most adults, a healthy BMI is between 18.5 and 24.9. However, optimal BMI may vary by age, sex, and ethnicity.

Q3: How often should I check my BMI?
A: For most adults, checking BMI annually is sufficient unless you're actively trying to lose or gain weight.

Q4: Are there limitations to BMI?
A: BMI doesn't distinguish between muscle and fat, and doesn't account for fat distribution, which is important for health risks.

Q5: Should children use this calculator?
A: No, children and teens need age- and sex-specific BMI percentiles rather than the adult categories.