BMI Calculator (USA)

BMI Formula (US Units):

\[ BMI = \frac{W_{lb}}{H_{in}^2} \times 703 \]

BMI Result:

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1. What is BMI (US Units)?

Definition: Body Mass Index (BMI) is a measure of body fat based on height and weight that applies to adult men and women.

Purpose: It provides a simple numeric measure of a person's thickness or thinness, allowing health professionals to discuss weight problems objectively.

2. How Does the Calculator Work?

The calculator uses the US customary units formula:

\[ BMI = \frac{W_{lb}}{H_{in}^2} \times 703 \]

Where:

\( BMI \) — Body Mass Index (unitless)
\( W_{lb} \) — Weight in pounds (lb)
\( H_{in} \) — Height in inches (in)
\( 703 \) — Conversion factor (kg/m² to lb/in²)

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

3. BMI Categories

Standard Categories:

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

4. Using the Calculator

Tips: Enter your weight in pounds and height in inches. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Why is there a 703 in the formula?
A: It's the conversion factor from kg/m² (metric BMI) to lb/in² (US units).

Q2: Is BMI accurate for everyone?
A: BMI is a screening tool but doesn't directly measure body fat. Athletes with high muscle mass may have high BMI without excess fat.

Q3: What's the difference between US and metric BMI?
A: The calculation is equivalent - this version just uses pounds and inches instead of kilograms and meters.

Q4: Can children use this calculator?
A: Children's BMI is interpreted differently using age- and sex-specific percentiles.

Q5: What are the limitations of BMI?
A: It doesn't account for muscle mass, bone density, overall body composition, or racial/ethnic differences.