How the BMI calculator works
Enter your height and weight in US or metric units and the tool calculates your body mass index, a number that relates weight to height. BMI is weight in kilograms divided by height in meters squared. The calculator also shows the standard adult category your number falls in and the weight range that corresponds to a healthy BMI for your height.
What BMI does and does not tell you
BMI is a quick, population level screening tool, not a diagnosis or a direct measure of body fat or health. Because it uses only height and weight, it can misclassify very muscular people as overweight and may read differently across ages, builds, and ethnic backgrounds. It is best treated as one rough signal among many, not a verdict.
The adult BMI categories
For adults, the commonly used bands are below 18.5 underweight, 18.5 to 24.9 healthy weight, 25 to 29.9 overweight, and 30 or above in the obesity range. These cutoffs are the same regardless of sex. They do not apply to children and teens, who use age and sex specific percentiles instead.
Using your result thoughtfully
If your BMI is outside the healthy band, treat it as a prompt to consider a conversation with a healthcare provider rather than a reason to make drastic changes on your own. A clinician can look at the fuller picture, including waist measurement, activity, diet, family history, and lab results. This calculator is for general information only and is not medical advice.
Frequently asked questions
How is BMI calculated? Weight in kilograms divided by the square of height in meters; the tool handles US units for you.
Is BMI accurate? It is a rough screening estimate, not a measure of body fat or health, and can misjudge muscular builds.
What is a healthy BMI? For adults, the commonly used healthy band is 18.5 to 24.9.
Related calculators: BMR, Body Fat, Ideal Weight.