BMI chart for adults

Category	BMI range	Health risk
Underweight	< 18.5	Increased risk
Normal weight	18.5 – 24.9	Minimal risk
Overweight	25.0 – 29.9	Moderate risk
Obese class I	30.0 – 34.9	High risk
Obese class II	35.0 – 39.9	Very high risk
Obese class III	≥ 40.0	Extremely high risk

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, a BMI between 18.5 and 24.9 is generally considered healthy by the World Health Organization. However, as you age, a slightly higher BMI (up to 27) may be acceptable and even protective against bone density loss.

How accurate is BMI?

BMI is a reasonable population-level indicator but is less precise at the individual level. Studies show it correctly identifies overweight or obesity in about 80% of cases. It is less accurate for athletes, elderly people, and certain ethnic groups.

What BMI is considered obese?

A BMI of 30 or above is classified as obese by the WHO. This is further divided into Class I (30–34.9), Class II (35–39.9), and Class III (40+, sometimes called severe or morbid obesity).

Can BMI be different for men and women?

The same BMI cutoffs apply to both men and women. However, at the same BMI, women typically have more body fat than men. Some researchers propose sex-specific BMI thresholds, but current WHO and CDC guidelines use the same ranges for all adults.

How do I lower my BMI?

To lower BMI, the core approach is reducing caloric intake while increasing physical activity. Even modest weight loss of 5–10% of body weight can have measurable health benefits. Speaking with a doctor or registered dietitian is the best way to create a safe, personalized plan.