Calculate your Body Mass Index (BMI) to determine if you are underweight, normal weight, overweight, or obese.
Body Mass Index is a quick screening number that compares your weight to your height. Enter your height and weight in metric or imperial units and the calculator returns your BMI and the standard category it falls into. It is the same formula used by the World Health Organization and most national health services.
BMI is a starting point, not a diagnosis. It does not measure body fat directly and does not distinguish muscle from fat, so very muscular people can read as "overweight" while the number can understate risk for others. Use it alongside measurements like waist circumference and advice from a health professional.
BMI is weight divided by height squared. The imperial version multiplies by 703 to convert units.
Metric: BMI = weight(kg) ÷ height(m)²Imperial: BMI = 703 × weight(lb) ÷ height(in)²Underweight = below 18.5Healthy weight = 18.5 to 24.9Overweight = 25 to 29.9Obese = 30 and aboveHeight squared: 1.75 × 1.75 = 3.0625. BMI = 70 ÷ 3.0625 = 22.9 — within the healthy range.
Height in inches: 69. Height squared: 4761. BMI = 703 × 185 ÷ 4761 = 27.3 — in the overweight range.
BMI = 45 ÷ (1.6 × 1.6) = 45 ÷ 2.56 = 17.6 — below 18.5, so the underweight category.
A 1.80 m athlete at 90 kg has a BMI of 27.8. The formula cannot tell that the extra weight is muscle, which is why BMI is only a screening tool.
For most adults, 18.5 to 24.9 is classed as a healthy weight. Below 18.5 is underweight, 25 to 29.9 is overweight and 30 or more is obese.
In metric, divide your weight in kilograms by your height in metres squared. In imperial, multiply your weight in pounds by 703 and divide by your height in inches squared.
Not very. Muscle is denser than fat, so people with a lot of muscle often have a high BMI despite low body fat. Body-composition methods are better for them.
Not directly. Children and teenagers are assessed with age- and sex-specific BMI percentile charts rather than the fixed adult categories.
The formula and adult cut-offs are the same for both, though women on average carry more body fat at the same BMI. Some populations use lower cut-offs — for example 23 for overweight in many Asian guidelines.
Where you carry weight matters. A large waist relative to your height signals more abdominal fat and higher risk even when BMI looks normal.
Yes. The calculation happens entirely in your browser and nothing is sent to a server.