BMI Calculator: Free Body Mass Index Tool
Use this free BMI calculator to find your Body Mass Index in seconds, in either metric or imperial units. Enter your height and weight, and the tool instantly shows your BMI number and the category it falls in, from underweight to obese. Body Mass Index is a quick screening estimate of body fat based on height and weight, used by doctors and coaches as a starting point for healthy-weight conversations.
How BMI Is Calculated
BMI uses a simple formula. In metric units it is your weight in kilograms divided by your height in meters squared (kg/m2). In imperial units it is 703 times your weight in pounds divided by your height in inches squared. For example, a person who is 178 cm tall and weighs 75 kg has a BMI of about 23.7, which falls in the normal-weight range.
BMI Categories
| BMI Range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to 24.9 | Normal weight |
| 25.0 to 29.9 | Overweight |
| 30.0 and above | Obese |
BMI is a screening tool, not a diagnosis. It does not measure body fat directly and can misclassify very muscular people or older adults. Treat it as a starting point and talk to a healthcare professional about your individual health.
Frequently Asked Questions: BMI
What is a healthy BMI?
A BMI between 18.5 and 24.9 is considered the normal, healthy-weight range for most adults. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or higher is classified as obese.
How do I calculate BMI by hand?
Divide your weight in kilograms by your height in meters squared. In imperial units, multiply your weight in pounds by 703, then divide by your height in inches squared. The calculator above does this instantly in either unit system.
Is BMI accurate for athletes?
Not always. Because muscle weighs more than fat, very muscular athletes can have a high BMI while carrying little body fat. BMI is a general screening tool and works best alongside other measures like waist circumference and body-fat percentage.
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