The average BMI for adults in the United States is roughly 29.5, which falls squarely in the overweight category and sits just below the obesity threshold of 30. Globally, the picture is different: the average BMI is about 24.2 for men and 24.4 for women, placing most of the world’s population near the upper end of the healthy weight range.
How BMI Is Calculated and Classified
BMI is your weight in kilograms divided by your height in meters squared. A 5’9″ person weighing 170 pounds, for example, has a BMI of about 25.1. The standard categories for adults 20 and older break down like this:
- Underweight: below 18.5
- Healthy weight: 18.5 to 24.9
- Overweight: 25 to 29.9
- Obesity (Class 1): 30 to 34.9
- Obesity (Class 2): 35 to 39.9
- Severe obesity (Class 3): 40 or higher
These cutoffs were set by the World Health Organization and are used by the CDC, most hospitals, and insurance companies. They apply to all adults regardless of sex, though health risks at each level can differ between men and women.
The U.S. Average: 29.5 and Rising
Between 2001 and 2018, the age-adjusted mean BMI in the U.S. climbed from about 27.7 to 29.5 for men and from 28.1 to 29.6 for women. That shift of nearly two full BMI points over less than two decades means the typical American adult moved closer to the obesity line.
The obesity rate itself tells an even sharper story. In the early 1960s, 13.4% of American adults had obesity. By 2021 to 2023, that figure had tripled to 40.3%, with an additional 31.7% classified as overweight. Severe obesity (a BMI of 40 or higher) went from under 1% to about 10% over the same period. The share of adults in the overweight range, interestingly, has barely changed at around 31%. What changed is that far more people moved past overweight into obesity.
Global Averages Vary Widely
The global average BMI of roughly 24.2 to 24.4 masks enormous regional differences. In central Africa and south Asia, the average for men is around 21.4, well within the healthy range. In Polynesia and Micronesia, the average for men is 29.2, and for women it reaches 32.2, which crosses into obesity. These gaps reflect differences in diet, physical activity, genetics, and economic development.
Most high-income countries, including the U.S., Canada, the U.K., and Australia, have national averages in the overweight range. The U.S. sits near the top among large nations but is not the highest globally.
What BMI Range Is Linked to the Lowest Health Risk
A large UK study tracking 3.6 million adults found a J-shaped relationship between BMI and the risk of death from most major causes, including cancer, heart disease, and respiratory disease. The lowest risk sat in the 21 to 25 range. Below 21, risk started to climb again, though the reasons are complex and can include underlying illness that causes weight loss.
This means the “average” BMI in the U.S. (around 29.5) is roughly four to five points above the range associated with the lowest mortality risk. That gap is one reason public health agencies treat rising national BMI as a concern, even though being slightly overweight carries a relatively modest increase in risk for most individuals.
Where BMI Falls Short
BMI cannot distinguish between fat, muscle, and bone. A muscular person who lifts weights regularly may have a BMI of 28 or 29 without carrying excess body fat. On the other hand, someone with a “normal” BMI can still have a high percentage of body fat, particularly if they’ve lost muscle mass with age. BMI also tells you nothing about where your fat is stored. Fat concentrated around the organs in your midsection (visceral fat) is more strongly linked to heart disease and diabetes than fat carried in the hips or thighs.
Because of these blind spots, waist circumference is often used as a complementary measure. A waist measurement above 35 inches for women or 40 inches for men signals higher risk for weight-related health problems, regardless of what the BMI number says. If your BMI falls in the healthy range but your waist exceeds those thresholds, the waist measurement is the more telling number for metabolic health.
How to Interpret Your Own Number
If you plug your height and weight into a BMI calculator and land between 18.5 and 24.9, you’re in the range associated with the fewest weight-related health risks. A number in the 25 to 29.9 range doesn’t automatically mean you’re unhealthy, especially if you’re physically active, have good blood pressure, and carry more muscle than average. Context matters.
A BMI of 30 or higher is the point where population-level data shows a more consistent increase in risks for conditions like type 2 diabetes, heart disease, sleep apnea, and certain cancers. The higher the number climbs above 30, the stronger that association becomes. But BMI is a screening tool, not a diagnosis. It flags who might benefit from a closer look at blood pressure, blood sugar, cholesterol, and waist size, rather than delivering a verdict on its own.