BMI Calculator
| Category | BMI Range |
|---|---|
| Underweight | Below 18.5 |
| Normal weight | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obese (Class I) | 30.0 – 34.9 |
| Obese (Class II) | 35.0 – 39.9 |
| Obese (Class III) | 40.0+ |
What BMI Measures
Body Mass Index (BMI) is a simple screening tool that uses your height and weight to estimate body fat levels. It's a population-level measurement, not a diagnostic tool — and it has well-documented limitations for individuals, particularly athletes, older adults, and people of different ethnicities.
The BMI Formula
BMI = weight (kg) / height (m)²
In US units: BMI = (weight in pounds × 703) / height in inches²
BMI categories (per CDC): Underweight: below 18.5 | Normal weight: 18.5–24.9 | Overweight: 25–29.9 | Obese: 30 and above
How to Use This Calculator
- Enter your height in feet and inches (or centimeters)
- Enter your weight in pounds (or kilograms)
- Click Calculate to see your BMI and weight category
Example Calculations
5'6" / 150 lbs: BMI = (150 × 703) / (66²) = 24.2 — Normal weight
5'10" / 200 lbs: BMI = (200 × 703) / (70²) = 28.7 — Overweight
5'4" / 120 lbs: BMI = (120 × 703) / (64²) = 20.6 — Normal weight
Limitations of BMI
BMI doesn't distinguish between muscle and fat. A highly muscular athlete may have a BMI in the "overweight" range while being extremely healthy. BMI also doesn't account for where fat is distributed — abdominal fat carries higher health risks than fat elsewhere, and BMI doesn't capture this. Doctors use BMI as one data point alongside waist circumference, blood pressure, cholesterol, and blood glucose for a complete health picture.