BMI Calculator
Check your body mass index (BMI) with metric or imperial units. Free online BMI calculator.
How It Works
What is BMI?
Body Mass Index (BMI) is a number calculated from your weight and height. It is a simple way to screen for weight categories that may affect health. BMI does not measure body fat directly, but it is a useful indicator for most adults. Health professionals use it as one of several tools to assess whether someone is underweight, normal weight, overweight, or obese.
The formula divides your weight by the square of your height. In metric units, weight is in kilograms and height in meters. In imperial units, weight is in pounds and height in inches, with a factor of 703 so the result matches the metric scale. Our calculator does this for you and also shows which category your result falls into.
BMI is intended for adults. It is not used to diagnose health conditions; it is a screening tool. For a full assessment, talk to a doctor or dietitian, who can consider age, sex, muscle mass, and other factors.
How to use this BMI calculator
- Choose your units: Metric (kg and cm) or Imperial (lb and inches).
- Enter your weight in the first field.
- Enter your height in the second field (height in cm for metric, or in inches for imperial).
- Click "Calculate BMI" to see your BMI and category.
BMI category table
| BMI range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal |
| 25 – 29.9 | Overweight |
| 30 and above | Obese |
Frequently Asked Questions
A BMI between 18.5 and 24.9 is generally considered the normal or healthy range for adults. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is obese. Health organizations use these ranges as screening tools; individual health depends on other factors too.
BMI is a useful population-level screening tool but does not distinguish between muscle and fat. Very muscular people may have a high BMI without excess body fat, and some people with a normal BMI may still have unhealthy fat levels. It does not account for age, sex, or body composition. For personal health decisions, use it as one indicator and consult a healthcare provider.
Use whichever you prefer. Select Metric for kilograms and centimeters, or Imperial for pounds and inches. The calculator converts internally and gives the same BMI scale; only the input units change.