BMI chart for adults

Category	BMI range	Screening category
Underweight	< 18.5	Use with other health information
Normal weight	18.5 – 24.9	Use with other health information
Overweight	25.0 – 29.9	Use with other health information
Obese class I	30.0 – 34.9	Use with other health information
Obese class II	35.0 – 39.9	Use with other health information
Obese class III	≥ 40.0	Use with other health information

What is BMI?

Body Mass Index (BMI) is a numerical measure calculated from a person's height and weight. It was developed by Belgian mathematician Adolphe Quetelet in the 1830s and remains one of the most widely used screening tools for identifying potential weight-related health issues.

BMI is calculated using a simple formula:

          Imperial: BMI = (weight in lbs × 703) ÷ (height in inches)²

          Metric: BMI = weight in kg ÷ (height in metres)²

Limitations of BMI

BMI is a useful screening tool but it has important limitations. It does not directly measure body fat, so it may overestimate fat in athletes with high muscle mass and underestimate it in older adults who have lost muscle. It also does not account for where fat is distributed in the body, which matters significantly for health risk.

Always consult a healthcare professional for a complete health assessment rather than relying on BMI alone.

BMI for children and teens

BMI is interpreted differently for people under 20 years old. Instead of fixed cutoff numbers, children's BMI is compared to growth charts based on age and sex. This calculator is designed for adults aged 20 and over.

How to interpret a BMI result thoughtfully

BMI is a screening measure that compares weight with height. It can be a useful starting point for adults because it is quick, consistent, and easy to track over time. It is not a diagnosis, and it does not directly measure body fat, fitness, nutrition, or overall health.

Context matters. Muscular people may have a higher BMI without excess body fat, and BMI may be less informative during pregnancy, for some older adults, and for children and teens, who use age- and sex-specific growth charts. A single number also cannot explain changes in sleep, medications, medical conditions, activity, or eating habits.

Use the result as a conversation starter, not a verdict. If you have a health concern or are considering a major change to your diet or exercise routine, speak with a qualified healthcare professional. This tool is for general education and is not medical advice.

Learn more in How to Calculate BMI and What It Can—and Cannot—Tell You.

Frequently asked questions

What is a good BMI for my age?

For adults aged 20 and over, standard BMI categories are commonly used as a screening reference. A BMI result is not a diagnosis, and the most useful interpretation depends on your health history, habits, and other clinical information.

How accurate is BMI?

BMI is a population-level screening measure. It does not directly measure body fat or account for muscle mass, health conditions, medications, or individual history, so it is less precise for making conclusions about one person.

What BMI is considered obese?

For adults, standard screening categories place a BMI of 30 or above in the obesity category. A healthcare professional can help interpret this in context rather than relying on a number alone.

Can BMI be different for men and women?

For adults, standard BMI categories do not vary by sex. BMI alone cannot describe body composition, so it should be considered alongside other relevant health information.

How do I lower my BMI?

If you are concerned about your weight or health, speak with a qualified healthcare professional. They can help you set a safe plan that accounts for your medical history, nutrition, activity, and goals.

Source: CDC BMI frequently asked questions. Reviewed September 2026.