Calculate your Body Mass Index (BMI) in metric or imperial units and learn which weight category you fall into based on World Health Organization ranges.
BMI is weight in kilograms divided by height in metres squared. It is a screening tool, not a diagnosis, and does not measure body composition.
Body Mass Index is calculated by dividing your weight in kilograms by the square of your height in metres (BMI = kg ÷ m²). In imperial units, the formula is weight in pounds divided by height in inches squared, multiplied by 703. The result is a single number used to screen for underweight, healthy weight, overweight, and obesity ranges. Our calculator accepts both metric and imperial units and returns your BMI along with the World Health Organization category it falls into.
Using World Health Organization ranges for adults, a BMI below 18.5 is classed as underweight, 18.5 to 24.9 as healthy weight, 25 to 29.9 as overweight, and 30 or above as obese. These thresholds are screening guidelines, not diagnoses, and the same number can mean different things for different bodies. They are most useful for spotting broad trends across populations and for prompting a closer look at your health rather than for labelling any individual.
No. BMI is a simple ratio of weight to height and cannot tell the difference between muscle and fat. Very muscular people, such as athletes, may register as overweight despite low body fat, while some people within a healthy BMI may carry excess fat. It also does not account for age, sex differences in body composition, or where fat is stored. Treat BMI as one quick screening tool to be considered alongside measures like body fat percentage, waist circumference, and overall fitness.
A BMI outside the healthy range is a prompt to look more closely, not a reason to panic. Consider it together with other indicators such as waist measurement, activity level, diet, and how you feel. If you are concerned, a doctor or registered dietitian can interpret your BMI in context and recommend safe, sustainable changes. Sudden or extreme measures are rarely helpful; gradual improvements to nutrition and activity tend to produce lasting results.
Yes. For children and teenagers, BMI is interpreted using age- and sex-specific percentile charts rather than the fixed adult categories, because growing bodies change composition with age. The calculator's standard categories apply to adults. For children, a pediatric BMI-for-age percentile from a healthcare provider is the appropriate measure.