Skip to content If you are looking up obesity risk, you may be hoping for a clear answer from one number. Adult BMI can be a starting point for discussion, but it cannot diagnose an individual or replace a fuller health assessment.
What BMI measures
For adults, BMI is calculated by dividing weight in kilograms by height in metres squared. Standard adult categories help describe weight relative to height. The CDC provides an adult BMI calculator for people age 20 and older and explains its screening categories. Children and teens need age- and sex-specific BMI-for-age references, not adult cutoffs.
BMI does not directly measure body fat, distinguish muscle from fat or bone, or show where fat is carried. A result cannot account for medical history, blood pressure, laboratory results, medications, or other factors. The CDC recommends considering BMI with other information when assessing an individual’s health.
Does BMI calculate obesity-related risk?
No. A BMI category is not a personal prediction of diabetes, heart disease, or another condition. A clinician may consider BMI alongside waist size and other health information, but a calculator using height and weight alone cannot provide a reliable individual disease-risk percentage. NIDDK explains that both BMI and waist size can contribute to a broader assessment and that BMI has limitations for some people.
Use a calculator to understand the measurement, not to label or diagnose yourself. If you have concerns about weight or health, a healthcare professional can decide what assessment is appropriate. Our weight-management guide and calculator collection provide general information only.
Short video: BMI screening basics
Frequently asked questions
Can BMI tell me whether I have obesity-related disease?
No. BMI is a screening measure and does not diagnose a disease or provide an individual risk prediction.
Does BMI work the same way for children?
No. Children and teens need BMI-for-age percentiles based on age and sex. Adult ranges should not be used for them.
What else may a clinician consider?
Depending on the person, assessment may include waist size, medical history, examination, blood pressure, and laboratory findings. A qualified professional can explain what is relevant.
Sources
Educational information only; not a diagnosis or personalized medical advice.
