BMI Calculator

What BMI means

Body Mass Index, or BMI, is a screening number that relates your weight to your height. It is widely used by doctors and public health agencies, including the CDC, as a quick way to flag weight categories that may raise health risks. BMI is not a direct measure of body fat, but for most adults it tracks reasonably well with body fatness.

How BMI is calculated

The formula is simple. With imperial units, divide your weight in pounds by your height in inches squared, then multiply by 703. With metric units, divide your weight in kilograms by your height in meters squared. A 5 foot 7 inch adult weighing 160 pounds works out to a BMI of about 25.1.

The standard weight categories

The CDC recognizes four adult BMI categories. Below 18.5 is underweight, 18.5 to 24.9 is a healthy weight, 25.0 to 29.9 is overweight, and 30.0 or above is obese. This calculator highlights the row your result lands in so you can see the context at a glance.

What BMI does not tell you

BMI treats everyone the same, but bodies are not all the same. It does not separate muscle from fat, so a heavily muscled athlete can land in the overweight range without being overfat. It also misses where fat is stored, and abdominal fat carries more health risk than fat on the hips or thighs. Older adults often lose muscle, so BMI can underestimate their body fat.

Using BMI the right way

Treat BMI as a starting point, not a verdict. A single number cannot capture fitness, diet, blood pressure, cholesterol, or family history. If your BMI falls outside the healthy range, or you have questions about your weight, talk to a healthcare provider who can look at the full picture rather than one screening number.