Metric example
At 180 cm and 75 kg: 75 ÷ (1.8 × 1.8) = 23.1. This is within the adult Healthy weight screening range.
Calculate adult body mass index with metric or US customary measurements, view the screening category, and estimate a healthy weight range for the entered height.
Body mass index compares weight with height to provide a general adult screening measure. It is widely used to group results into broad weight categories, but it does not directly measure body fat, fitness, fat distribution, or overall health.
BMI = weight (kg) ÷ height (m)²CalcRocket converts US inputs with exact unit conversion constants before calculating; 703 is the familiar rounded customary formula factor.
BMI = 703 × weight (lb) ÷ height (in)²These screening categories apply to adults. Pediatric BMI requires age- and sex-specific percentiles.
| Category | BMI range | Additional detail |
|---|---|---|
| Underweight | Below 18.5 | — |
| Healthy weight | 18.5 to below 25 | Displayed as 18.5–24.9 |
| Overweight | 25 to below 30 | — |
| Obesity | 30 or higher | Class I: 30–34.9; Class II: 35–39.9; Class III: 40+ |
The estimate applies BMI 18.5 and 24.9 to the entered height squared, then converts the resulting weights for the alternate unit system. It is a mathematical screening range, not an individualized target or treatment recommendation.
BMI can be useful for broad screening, but it leaves out important individual information.
At 180 cm and 75 kg: 75 ÷ (1.8 × 1.8) = 23.1. This is within the adult Healthy weight screening range.
At 5 ft 10 in and 180 lb: the BMI is approximately 25.8. This is within the adult Overweight screening range.
Body mass index, or BMI, is a screening measure that relates weight to height. It does not directly measure body fat and is not a diagnosis.
Metric BMI divides weight in kilograms by height in meters squared. US customary inputs are converted to consistent metric units before the same calculation is performed.
For adults, the commonly used healthy-weight screening range is BMI 18.5 to below 25. Individual health cannot be determined from BMI alone.
No. BMI does not directly measure body composition or fat distribution. It is a population-level screening measure with important individual limitations.
BMI cannot distinguish muscle from fat, so muscular athletes may have a higher BMI without having excess body fat.
No. These categories are intended for adults. BMI for children and teenagers must be interpreted using age- and sex-specific percentiles by a qualified healthcare professional.
The calculator applies BMI values 18.5 and 24.9 to the entered height squared. The result is an estimate, not a personal weight recommendation.
The standard adult BMI formula and category cutoffs are the same, but BMI does not capture differences in body composition, age, sex, ethnicity, pregnancy, or individual health.