Understanding your calculation
Method, example and limitations
How the calculation works
Adult BMI divides weight in kilograms by height in meters squared. This page uses adult categories for people aged 20 or older. Category boundaries use the unrounded BMI; the displayed number is rounded, so a value very close to a boundary can look like the next category.
Example to check
For a 30-year-old adult weighing 72 kg and measuring 180 cm, first convert height to 1.8 m. BMI = 72 ÷ 1.8² = 22.2 when rounded to one decimal. Height and weight must be positive and within the displayed input ranges.
Before using the result
BMI is a screening measure, not a diagnosis or a target weight prescription. Children and teens require age- and sex-specific assessment. Pregnancy, muscle mass and individual health circumstances can make adult categories less informative. Discuss personal health decisions with a clinician.
CDC: Adult BMI categories · Calculation methodology · Report a result that needs review