What Is the BMI Calculator?
The Body Mass Index (BMI) Calculator is a standardized clinical screening tool that measures body fatness based on an individual’s weight relative to their height. Developed by Belgian statistician Adolphe Quetelet and standardized by the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC), BMI serves as a universal benchmark for evaluating weight categories and health indicators.
How to Calculate Body Mass Index
The BMI formula evaluates your weight and height according to standardized international ratios:
- Metric Formula:
BMI = Weight (kg) / [Height (m)]² - Imperial Formula:
BMI = [Weight (lbs) × 703] / [Height (inches)]²
Standard WHO & CDC Weight Classifications
The World Health Organization classifies adult BMI values into four primary categories:
- Underweight: BMI less than 18.5
- Normal / Healthy Weight: BMI between 18.5 and 24.9
- Overweight: BMI between 25.0 and 29.9
- Obesity: BMI of 30.0 or higher
How to Use the BMI Calculator
- Step 1: Select your preferred unit system (Imperial for pounds, feet, and inches, or Metric for kilograms and centimeters).
- Step 2: Enter your body weight and measured height.
- Step 3: Review your instantaneous BMI score, your official clinical weight tier, and your personal healthy weight target range.
Frequently Asked Questions
What is BMI Prime?
BMI Prime is the ratio of your calculated BMI to the upper limit of the normal weight threshold (BMI 25.0). A BMI Prime of 1.0 represents the upper normal boundary. Values below 1.0 indicate normal or underweight status, while values above 1.0 indicate overweight status.
Is BMI accurate for athletes and bodybuilders?
BMI calculates total body mass relative to height, but does not distinguish between lean skeletal muscle mass and adipose fat tissue. Highly muscular athletes may register as overweight or obese despite maintaining low body fat percentages. In such cases, waist-to-hip ratio and body fat calipers provide additional context.