Calculate Your BMI

What is BMI?

Body Mass Index (BMI) is a person's weight in kilograms divided by the square of height in meters. It is an inexpensive and easy screening method for weight category—underweight, healthy weight, overweight, and obesity.

BMI does not measure body fat directly, but BMI is moderately correlated with more direct measures of body fat. Furthermore, BMI appears to be as strongly correlated with various metabolic and disease outcomes as are these more direct measures of body fatness.

BMI Formula:
BMI = weight (kg) / [height (m)]²
or
BMI = (weight (lbs) / [height (inches)]²) × 703

BMI Categories (Adults)

  • Underweight: BMI less than 18.5
  • Normal weight: BMI 18.5 to 24.9
  • Overweight: BMI 25 to 29.9
  • Obesity (Class I): BMI 30 to 34.9
  • Obesity (Class II): BMI 35 to 39.9
  • Extreme Obesity (Class III): BMI 40 and above

How to Use This BMI Calculator

  1. Select your preferred unit system (Metric or Imperial)
  2. Enter your height in centimeters or inches
  3. Enter your weight in kilograms or pounds
  4. Click "Calculate BMI" to see your results
  5. Review your BMI value and category

The calculator will instantly show your BMI value and classify it into one of the standard weight categories. Your result will be highlighted in the BMI ranges table for easy reference.

When to Use BMI

BMI is a useful tool for:

  • Initial screening for weight-related health risks
  • Tracking weight changes over time
  • Population health studies and statistics
  • General health assessments
  • Setting realistic weight management goals

Limitations of BMI

While BMI is a useful screening tool, it has important limitations:

  • Doesn't distinguish muscle from fat: Athletes and very muscular people may have high BMI despite low body fat
  • Doesn't account for body composition: Two people with the same BMI can have very different body fat percentages
  • Age and sex differences: Women tend to have more body fat than men, and older people tend to have more body fat than younger adults
  • Not accurate for all populations: Different ethnic groups may have different health risks at the same BMI
  • Pregnancy: BMI calculations are not applicable during pregnancy
  • Children and teens: BMI for children requires age and sex-specific percentiles

Next Steps

If your BMI is outside the normal range, consider consulting with a healthcare professional for a comprehensive health assessment. They can provide personalized advice based on your overall health, body composition, and lifestyle.

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