BMI Calculator

A BMI calculator estimates body mass index — a quick screening number that relates your weight to your height. Enter your height and weight in metric or imperial units and the tool returns your BMI along with the standard category it falls into: underweight, healthy weight, overweight, or obese. It is the same formula clinics use for a fast first look at whether weight may be a health consideration.

BMI is popular because it is simple and requires nothing but a scale and a tape measure, making it a reasonable starting point for most adults. This calculator does the arithmetic for you in either unit system, so there is no need to convert centimeters to meters or pounds to a height-squared figure by hand.

Your measurements are processed entirely in your browser and never uploaded, so you can check your number — or model a goal weight — privately.

BMI is calculated as weight in kilograms divided by height in meters squared (kg/m²). In imperial units the equivalent is 703 × weight in pounds ÷ height in inches squared. The standard adult categories are: under 18.5 is underweight, 18.5–24.9 is a healthy weight, 25–29.9 is overweight, and 30 or above is classed as obese.

BMI is a screening tool, not a diagnosis. It does not distinguish muscle from fat, so very muscular people can read as “overweight” despite low body fat, and it can underestimate body fat in older adults who have lost muscle. It also was not designed for children, pregnant people, or athletes, who need age-, sex-, or composition-specific measures.

Treat your BMI as one data point among several — waist circumference, activity level, blood pressure, and how you feel all matter. If your number sits outside the healthy range or you are unsure what it means for you, a clinician can interpret it in the context of your overall health.