Calculate your Body Mass Index in metric or imperial units.
Choose imperial (pounds, feet and inches) or metric (kilograms, centimeters) with the toggle, enter your weight and height, and your BMI and category appear immediately. Both unit systems give the same answer for the same person.
Body Mass Index (BMI) is weight (kg) ÷ height (m)². For imperial units, the equivalent is 703 × weight (lb) ÷ height (in)². The result is rounded to one decimal place.
| Category | BMI |
|---|---|
| Underweight | under 18.5 |
| Normal weight | 18.5 to 24.9 |
| Overweight | 25.0 to 29.9 |
| Obese | 30.0 and above |
These are the standard adult cutoffs used by major health organizations. This calculator shows a single "Obese" band for everything from 30 up.
You can also work backward. At 5 ft 7 in, a BMI between 18.5 and 24.9 corresponds to roughly 118 to 159 lb. At 170 cm it corresponds to roughly 53.5 to 72 kg.
BMI uses only height and weight, so it can't distinguish muscle from fat or show where weight is carried. Very muscular people can land in the overweight range with low body fat, and older adults can have a normal BMI with little muscle. Some health organizations also use different cutoffs for certain populations.
BMI for children and teens is interpreted with percentiles for age and sex, so the adult categories above don't apply to them. It is best treated as one screening number alongside blood pressure, waist measurement, fitness, family history and how you feel.
Not necessarily. It is a statistical category, not a measure of health. Someone in the normal range can still have health risks, and someone outside it can be perfectly healthy.
Small differences usually come from rounding of height or unit conversion. The formula itself is standard.
If it surprises you or you're worried about your weight, talk to a doctor or other healthcare provider. To convert your height or weight between systems first, use the unit converter, and for other percentages in daily life see the percentage calculator.
BMI is a general screening tool and doesn't account for muscle mass, bone density, age, or body composition. It is not a diagnosis — talk to a healthcare provider for a full picture of your health.