Calculate your body mass index in metric or imperial units, see where you land on the scale, and find the healthy weight range for your height.
BMI is a screening tool, not a diagnosis or a measure of body fat. It can misclassify very muscular people and doesn't account for age, sex, or where fat is stored. This tool is for educational purposes only and is not medical advice; talk to a healthcare professional about what's healthy for you.
Body mass index compares your weight to your height. In metric units, BMI is your weight in kilograms divided by your height in metres squared. In imperial units, it's 703 times your weight in pounds divided by your height in inches squared — the 703 factor simply converts the result to the same scale, so both methods give the same number.
Because it needs only height and weight, BMI is quick and widely used as a first-pass screen. What it can't see is what your weight is made of, which is why it's a starting point rather than the whole picture.
For adults, the standard ranges are: below 18.5 is underweight, 18.5 to 24.9 is the normal or healthy range, 25 to 29.9 is overweight, and 30 or above falls into the obesity range. These cut-offs come from population studies linking BMI to health risk, so they describe statistical patterns across groups rather than a verdict on any one person.
Two people with the same BMI can be in very different health, so treat your category as one data point alongside things like waist size, fitness, blood pressure, and how you feel.
Because the normal BMI band is a range, it maps to a range of weights for any given height — the calculator shows yours above. For a person 175 cm (about 5'9") tall, a BMI of 18.5 to 24.9 corresponds to roughly 57 to 76 kg (125 to 168 lb).
Seeing the range rather than a single "ideal" number is more realistic: healthy bodies come in a span of weights, and where you sit within or near the range depends on your build and muscle mass.
BMI counts all weight the same, so it can't distinguish muscle from fat. A muscular athlete may register as "overweight" despite low body fat, while someone in the normal range can still carry excess fat with little muscle. It also says nothing about fat distribution, even though fat around the waist carries more health risk than fat on the hips and thighs.
Age, sex, and ethnicity matter too — the same BMI can mean different risk levels across populations. For a fuller picture, pair BMI with a body-fat estimate and a waist measurement.
This calculator is for adults. BMI works differently for anyone under 20: a child's healthy range changes constantly with age and differs by sex, so a single adult cut-off doesn't apply. Instead, a child's BMI is plotted on age- and sex-specific growth charts and reported as a percentile compared with other children of the same age.
Because of that, a child's or teen's BMI should be interpreted by a pediatrician or healthcare provider using those growth charts — not with adult categories. If you're checking a young person's growth, please speak with their doctor rather than relying on an adult tool.
Divide your weight in kilograms by your height in metres squared, or multiply 703 times your weight in pounds divided by your height in inches squared. Enter your numbers above and the calculator does it in either unit system.
For adults, a BMI between 18.5 and 24.9 is generally considered the healthy range. It's a guideline based on population data, not a personal diagnosis.
Not always. Because muscle weighs more than fat, very muscular people can have a high BMI while carrying little fat. For them, a body-fat measurement is more informative.
The adult formula and categories are the same for both. Women tend to carry more body fat than men at the same BMI, which is one reason BMI is a screen rather than a precise body-fat measure.
No. For anyone under 20, BMI is interpreted using age- and sex-specific percentiles on growth charts. Ask a pediatrician to assess a child's or teen's BMI rather than using adult ranges.