How is BMI calculated?
Divide weight in kilograms by height in meters squared: BMI = kg / m². For centimeters, BMI = kg × 10,000 / cm². U.S. units are converted precisely before calculation. See the BMI formula and examples.
Adult body mass index
BMI Calculator
Calculate body mass index (BMI) using height and weight. For adults age 20 or older, see the corresponding CDC adult BMI screening category.
Results
Adult BMI screening result
Body mass index (BMI), kg/m²—Confirm the adult age range to begin.
- CDC adult BMI category
- —
Screening information only
The CDC category is a screening classification, not a medical diagnosis. BMI does not account for individual differences in muscle, bone or body-fat distribution. If you need an assessment of your health, consider discussing your circumstances with a qualified healthcare professional.
CDC adult BMI categories
| Category | BMI (kg/m²) |
|---|---|
| Underweight | Below 18.5 |
| Healthy weight | 18.5 to less than 25 |
| Overweight | 25 to less than 30 |
| Obesity | 30 or greater |
Source: CDC Adult BMI Categories.
Why is BMI only a screening measure?
BMI uses height and weight but does not directly measure body fat, its distribution, or every factor relevant to a person's health. A BMI category alone cannot diagnose a condition. CDC: About BMI.
Why can 25.0 have a different category?
BMI is displayed to one decimal place, but the CDC screening category uses the unrounded number. A computed value such as 24.975 displays as 25.0 but is still below the 25 threshold. A rounding note explains this beside relevant results.
Do BMI ranges differ for adult men and women?
The CDC uses the same primary adult category cutoffs for ages 20 and older regardless of sex, age or race. Interpretation of an individual's health still requires additional information; there is no sex-specific diagnosis here.
Children, teens and pregnancy
Ages 2–19 need BMI-for-age percentiles rather than adult categories. This calculator does not assess pregnancy weight gain; CDC pregnancy guidance uses pre-pregnancy BMI for that context.
Privacy, sources and limits
The calculation uses measurements only in the active browser page; no account or app-owned history is kept. Copy, CSV and Print / Save PDF can create copies on your device when chosen. Read About and the privacy/limits disclosure or the Manual. Mycelgrid is not affiliated with or endorsed by CDC or NIST.