Weight check
BMI calculator for adults
Body mass index compares your weight with your height. It is quick and widely used as a first screen, and it has clear limits. Here is your number and how to read it.
Your height and weight
For adults 20 and older. Nothing you enter leaves this page.
What you will see
Your BMI, its CDC category, and what BMI can and cannot tell you.
Educational only, not medical advice. BMI is a screening measure, not a diagnosis.
Source
Formula: weight in kilograms divided by height in meters squared. Categories: CDC, for adults 20 and older.
Validated in
The same categories apply to all adults 20 and older, regardless of age, sex or race (CDC).
Limits
Does not separate fat from muscle or bone, and does not show where fat is carried. Not for children, teens or pregnancy.
BMI categories for adults
CDC uses these categories for adults 20 and older, the same for men and women (CDC):
| BMI | Category |
|---|---|
| Under 18.5 | Underweight |
| 18.5 to under 25 | Healthy weight |
| 25 to under 30 | Overweight |
| 30 to under 35 | Obesity, class 1 |
| 35 to under 40 | Obesity, class 2 |
| 40 or higher | Obesity, class 3 (severe obesity) |
How BMI is calculated
BMI is weight in kilograms divided by height in meters squared (CDC). In US units, that is 703 times weight in pounds, divided by height in inches squared. For example, 5 ft 9 in (69 inches) and 154 lb gives 703 × 154 ÷ 69² = 22.7.
What BMI cannot tell you
CDC is direct about the limits. BMI does not distinguish between fat, muscle and bone, does not show what types of fat a person has, and does not show where in the body fat is carried (CDC). It is a screening measure, and for any one person it should be considered alongside medical history, habits, a physical exam and lab results (CDC) (CDC).
In practice that means a muscular person can land in the overweight range without excess fat, and a person in the healthy range can still carry more fat around the waist than the number suggests.
For where fat sits, use the waist-to-height ratio calculator. If your BMI is 30 or higher, see the weight loss program check.
Where BMI shows up in risk checks
- Diabetes: the ADA risk test gives points for BMI, from 0 below 25 up to 3 at 40 or more (ADA). The ADA recommends earlier diabetes testing for adults with overweight or obesity plus another risk factor, and uses a lower BMI line of 23 for Asian American adults (ADA Standards 2026). Try the diabetes risk test.
- Sleep apnea: a BMI over 35 is one of the eight STOP-Bang items (Chung 2016). See the sleep apnea page.
Common questions
Is BMI different for men and women?
No. CDC uses the same adult categories regardless of age, sex or race (CDC). Body fat at a given BMI can differ between people, which is one of BMI's limits.
Can I use this for my child?
No. For children and teens, CDC compares BMI with others of the same age and sex using growth charts, so the adult categories do not apply (CDC). See the child high BMI check for what the USPSTF advises.
What is a healthy BMI?
CDC calls 18.5 to under 25 the healthy weight range for adults (CDC).
See also which numbers each check needs.
Sources
- Centers for Disease Control and Prevention. Adult BMI Categories. www.cdc.gov/bmi/adult-calculator/bmi-categories.html
- Centers for Disease Control and Prevention. About Body Mass Index (BMI). www.cdc.gov/bmi/about/index.html
- American Diabetes Association Professional Practice Committee. 2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes 2026. Diabetes Care. 2026;49(Suppl 1):S27-S49. doi.org/10.2337/dc26-S002
- American Diabetes Association. Type 2 Diabetes Risk Test. diabetes.org/diabetes-risk-test
- Chung F, Abdullah HR, Liao P. STOP-Bang Questionnaire: A Practical Approach to Screen for Obstructive Sleep Apnea. Chest. 2016;149(3):631-638. doi.org/10.1378/chest.15-0903
Written and maintained by the uncovermyrisk.com editorial team. We do not have a medical reviewer; every claim links to its primary source above. Last reviewed: 2026-10-30. Spotted an error? See About.