BMI Calculator
Body mass index in metric (kg / cm) or imperial (lb / ft / in), with the healthy weight range for your height
BMI compares your weight to your height using a simple formula that has been used in population health screening for decades. It's quick to calculate and useful as a starting point, but it's a two-variable estimate, not a measurement of body fat, muscle, or overall health, so this page also shows the healthy weight range for your specific height and what BMI does and doesn't tell you.
For adults 20 and older, the CDC uses the same BMI categories regardless of age or sex, so these two fields do not change an adult result. Age is only used to flag people under 20, whose BMI is read differently.
BMI = weight (kg) ÷ height (m)²Weight at Each BMI Category, for Your Height
Based on the height you entered above.
| BMI Reaches | At This Weight |
|---|---|
| 18.5 | 56.7 kg |
| 25.0 | 76.6 kg |
| 30.0 | 91.9 kg |
| 35.0 | 107.2 kg |
| 40.0 | 122.5 kg |
BMI Categories for Adults
For adults 20 and older, the CDC groups BMI into the categories below. The same cutoffs apply regardless of age or sex.
Metric vs Imperial
Both systems give the same BMI. The metric formula divides weight in kilograms by height in meters squared. The imperial formula multiplies weight in pounds by 703 and divides by height in inches squared. The 703 is just the unit conversion.
Worked Examples
703 × 160 ÷ 69² = 23.6, which falls in the healthy weight category (18.5 to 24.9). For this height, the healthy range runs from about 125 lb to 169 lb.
703 × 140 ÷ 64² = 24.0, still inside the healthy category but closer to its upper edge of 24.9 than Example 1 is, despite weighing less in absolute pounds, because the height is shorter.
Same height as Example 1 but 40 lb heavier: 703 × 200 ÷ 69² = 29.5, in the overweight category and about 4.5 points below the obesity threshold of 30. This shows how much a fixed weight difference shifts BMI once height is held constant.
Limitations of BMI
BMI uses only height and weight. It cannot tell muscle from fat, does not show where body fat is carried, and does not account for age-related changes, pregnancy, or differences between populations. A very muscular person can have a high BMI without excess body fat, and someone with a BMI in the healthy range can still have health risks. For people under 20, BMI is read as a percentile for age and sex rather than with the adult cutoffs.
Other Ways to Screen Body Composition
Because BMI can't distinguish fat from muscle or show where fat is stored, some clinicians also look at waist circumference, waist-to-hip ratio, or body fat percentage from methods like skinfold calipers or bioelectrical impedance scales, alongside BMI rather than instead of it. None of these on their own fully captures health risk, which is one reason BMI is best treated as a starting conversation point, not a final answer.
Categories follow the CDC: Adult BMI Categories. This tool is for general information only and is not medical advice.